---
title: CERN Open Hardware Licence Version 2 - Weakly Reciprocal
spdx-id: CERN-OHL-W-2.0
nickname: CERN OHL v2 Weakly Reciprocal

description: Permissions of this weakly-reciprocal license are conditioned on making available complete sources of licensed works and modifications under the same license. Notices must be preserved. Contributors provide an express grant of patent rights. However, a larger work using the licensed work through interfaces provided by the licensed work may be distributed under different terms and without sources for the larger work.

how: Create a text file (typically named LICENSE or LICENSE.txt) in the root of your source code and copy the text of the license into the file.

note: 'CERN <a href="https://ohwr.org/project/cernohl/wikis/uploads/c2e5e9d297949b5c2d324a6cbf6adda0/cern_ohl_w_v2_howto.pdf">recommends</a> adding the following information in the source files: copyright and license notice, a disclaimer of warranties and a source location. You can also include the source location in a part of the design which will be visible in the end product.'

using:
  Simple PCIe FMC carrier: https://ohwr.org/project/spec/blob/master/LICENSES/CERN-OHL-W-2.0.txt
  GProcessor8Bits: https://github.com/JonathSpirit/GP8B/blob/master/LICENSE
  FPGA Cores: https://github.com/suoto/fpga_cores/blob/master/LICENSE

permissions:
  - commercial-use
  - modifications
  - distribution
  - private-use
  - patent-use

conditions:
  - include-copyright
  - document-changes
  - disclose-source
  - same-license--library

limitations:
  - liability
  - warranty

---
CERN Open Hardware Licence Version 2 - Weakly Reciprocal


Preamble

CERN has developed this licence to promote collaboration among hardware
designers and to provide a legal tool which supports the freedom to use,
study, modify, share and distribute hardware designs and products based on
those designs. Version 2 of the CERN Open Hardware Licence comes in three
variants: CERN-OHL-P (permissive); and two reciprocal licences: this licence,
CERN-OHL-W (weakly reciprocal) and CERN-OHL-S (strongly reciprocal).

The CERN-OHL-W is copyright CERN 2020. Anyone is welcome to use it, in
unmodified form only.

Use of this Licence does not imply any endorsement by CERN of any Licensor or
their designs nor does it imply any involvement by CERN in their development.


1 Definitions

  1.1 'Licence' means this CERN-OHL-W.

  1.2 'Compatible Licence' means

       a) any earlier version of the CERN Open Hardware licence, or

       b) any version of the CERN-OHL-S or the CERN-OHL-W, or

       c) any licence which permits You to treat the Source to which it
          applies as licensed under CERN-OHL-S or CERN-OHL-W provided that on
          Conveyance of any such Source, or any associated Product You treat
          the Source in question as being licensed under CERN-OHL-S or
          CERN-OHL-W as appropriate.

  1.3 'Source' means information such as design materials or digital code
      which can be applied to Make or test a Product or to prepare a Product
      for use, Conveyance or sale, regardless of its medium or how it is
      expressed. It may include Notices.

  1.4 'Covered Source' means Source that is explicitly made available under
      this Licence.

  1.5 'Product' means any device, component, work or physical object, whether
      in finished or intermediate form, arising from the use, application or
      processing of Covered Source.

  1.6 'Make' means to create or configure something, whether by manufacture,
      assembly, compiling, loading or applying Covered Source or another
      Product or otherwise.

  1.7 'Available Component' means any part, sub-assembly, library or code
      which:

       a) is licensed to You as Complete Source under a Compatible Licence; or

       b) is available, at the time a Product or the Source containing it is
          first Conveyed, to You and any other prospective licensees

           i) with sufficient rights and information (including any
              configuration and programming files and information about its
              characteristics and interfaces) to enable it either to be Made
              itself, or to be sourced and used to Make the Product; or
          ii) as part of the normal distribution of a tool used to design or
              Make the Product.

  1.8 'External Material' means anything (including Source) which:

       a) is only combined with Covered Source in such a way that it
          interfaces with the Covered Source using a documented interface
          which is described in the Covered Source; and

       b) is not a derivative of or contains Covered Source, or, if it is, it
          is solely to the extent necessary to facilitate such interfacing.

  1.9 'Complete Source' means the set of all Source necessary to Make a
      Product, in the preferred form for making modifications, including
      necessary installation and interfacing information both for the Product,
      and for any included Available Components.  If the format is
      proprietary, it must also be made available in a format (if the
      proprietary tool can create it) which is viewable with a tool available
      to potential licensees and licensed under a licence approved by the Free
      Software Foundation or the Open Source Initiative. Complete Source need
      not include the Source of any Available Component, provided that You
      include in the Complete Source sufficient information to enable a
      recipient to Make or source and use the Available Component to Make the
      Product.

 1.10 'Source Location' means a location where a Licensor has placed Covered
      Source, and which that Licensor reasonably believes will remain easily
      accessible for at least three years for anyone to obtain a digital copy.

 1.11 'Notice' means copyright, acknowledgement and trademark notices, Source
      Location references, modification notices (subsection 3.3(b)) and all
      notices that refer to this Licence and to the disclaimer of warranties
      that are included in the Covered Source.

 1.12 'Licensee' or 'You' means any person exercising rights under this
      Licence.

 1.13 'Licensor' means a natural or legal person who creates or modifies
      Covered Source. A person may be a Licensee and a Licensor at the same
      time.

 1.14 'Convey' means to communicate to the public or distribute.


2 Applicability

  2.1 This Licence governs the use, copying, modification, Conveying of
      Covered Source and Products, and the Making of Products. By exercising
      any right granted under this Licence, You irrevocably accept these terms
      and conditions.

  2.2 This Licence is granted by the Licensor directly to You, and shall apply
      worldwide and without limitation in time.

  2.3 You shall not attempt to restrict by contract or otherwise the rights
      granted under this Licence to other Licensees.

  2.4 This Licence is not intended to restrict fair use, fair dealing, or any
      other similar right.


3 Copying, Modifying and Conveying Covered Source

  3.1 You may copy and Convey verbatim copies of Covered Source, in any
      medium, provided You retain all Notices.

  3.2 You may modify Covered Source, other than Notices, provided that You
      irrevocably undertake to make that modified Covered Source available
      from a Source Location should You Convey a Product in circumstances
      where the recipient does not otherwise receive a copy of the modified
      Covered Source. In each case subsection 3.3 shall apply.

      You may only delete Notices if they are no longer applicable to the
      corresponding Covered Source as modified by You and You may add
      additional Notices applicable to Your modifications.

  3.3 You may Convey modified Covered Source (with the effect that You shall
      also become a Licensor) provided that You:

       a) retain Notices as required in subsection 3.2;

       b) add a Notice to the modified Covered Source stating that You have
          modified it, with the date and brief description of how You have
          modified it;

       c) add a Source Location Notice for the modified Covered Source if You
          Convey in circumstances where the recipient does not otherwise
          receive a copy of the modified Covered Source; and

       d) license the modified Covered Source under the terms and conditions
          of this Licence (or, as set out in subsection 8.3, a later version,
          if permitted by the licence of the original Covered Source). Such
          modified Covered Source must be licensed as a whole, but excluding
          Available Components contained in it or External Material to which
          it is interfaced, which remain licensed under their own applicable
          licences.


4 Making and Conveying Products

  4.1 You may Make Products, and/or Convey them, provided that You either
      provide each recipient with a copy of the Complete Source or ensure that
      each recipient is notified of the Source Location of the Complete
      Source. That Complete Source includes Covered Source and You must
      accordingly satisfy Your obligations set out in subsection 3.3. If
      specified in a Notice, the Product must visibly and securely display the
      Source Location on it or its packaging or documentation in the manner
      specified in that Notice.

  4.2 Where You Convey a Product which incorporates External Material, the
      Complete Source for that Product which You are required to provide under
      subsection 4.1 need not include any Source for the External Material.

  4.3 You may license Products under terms of Your choice, provided that such
      terms do not restrict or attempt to restrict any recipients' rights
      under this Licence to the Covered Source.


5 Research and Development

You may Convey Covered Source, modified Covered Source or Products to a legal
entity carrying out development, testing or quality assurance work on Your
behalf provided that the work is performed on terms which prevent the entity
from both using the Source or Products for its own internal purposes and
Conveying the Source or Products or any modifications to them to any person
other than You. Any modifications made by the entity shall be deemed to be
made by You pursuant to subsection 3.2.


6 DISCLAIMER AND LIABILITY

  6.1 DISCLAIMER OF WARRANTY -- The Covered Source and any Products are
      provided 'as is' and any express or implied warranties, including, but
      not limited to, implied warranties of merchantability, of satisfactory
      quality, non-infringement of third party rights, and fitness for a
      particular purpose or use are disclaimed in respect of any Source or
      Product to the maximum extent permitted by law. The Licensor makes no
      representation that any Source or Product does not or will not infringe
      any patent, copyright, trade secret or other proprietary right. The
      entire risk as to the use, quality, and performance of any Source or
      Product shall be with You and not the Licensor. This disclaimer of
      warranty is an essential part of this Licence and a condition for the
      grant of any rights granted under this Licence.

  6.2 EXCLUSION AND LIMITATION OF LIABILITY -- The Licensor shall, to the
      maximum extent permitted by law, have no liability for direct, indirect,
      special, incidental, consequential, exemplary, punitive or other damages
      of any character including, without limitation, procurement of
      substitute goods or services, loss of use, data or profits, or business
      interruption, however caused and on any theory of contract, warranty,
      tort (including negligence), product liability or otherwise, arising in
      any way in relation to the Covered Source, modified Covered Source
      and/or the Making or Conveyance of a Product, even if advised of the
      possibility of such damages, and You shall hold the Licensor(s) free and
      harmless from any liability, costs, damages, fees and expenses,
      including claims by third parties, in relation to such use.


7 Patents

  7.1 Subject to the terms and conditions of this Licence, each Licensor
      hereby grants to You a perpetual, worldwide, non-exclusive, no-charge,
      royalty-free, irrevocable (except as stated in subsections 7.2 and 8.4)
      patent licence to Make, have Made, use, offer to sell, sell, import, and
      otherwise transfer the Covered Source and Products, where such licence
      applies only to those patent claims licensable by such Licensor that are
      necessarily infringed by exercising rights under the Covered Source as
      Conveyed by that Licensor.

  7.2 If You institute patent litigation against any entity (including a
      cross-claim or counterclaim in a lawsuit) alleging that the Covered
      Source or a Product constitutes direct or contributory patent
      infringement, or You seek any declaration that a patent licensed to You
      under this Licence is invalid or unenforceable then any rights granted
      to You under this Licence shall terminate as of the date such process is
      initiated.


8 General

  8.1 If any provisions of this Licence are or subsequently become invalid or
      unenforceable for any reason, the remaining provisions shall remain
      effective.

  8.2 You shall not use any of the name (including acronyms and
      abbreviations), image, or logo by which the Licensor or CERN is known,
      except where needed to comply with section 3, or where the use is
      otherwise allowed by law. Any such permitted use shall be factual and
      shall not be made so as to suggest any kind of endorsement or
      implication of involvement by the Licensor or its personnel.

  8.3 CERN may publish updated versions and variants of this Licence which it
      considers to be in the spirit of this version, but may differ in detail
      to address new problems or concerns. New versions will be published with
      a unique version number and a variant identifier specifying the variant.
      If the Licensor has specified that a given variant applies to the
      Covered Source without specifying a version, You may treat that Covered
      Source as being released under any version of the CERN-OHL with that
      variant. If no variant is specified, the Covered Source shall be treated
      as being released under CERN-OHL-S. The Licensor may also specify that
      the Covered Source is subject to a specific version of the CERN-OHL or
      any later version in which case You may apply this or any later version
      of CERN-OHL with the same variant identifier published by CERN.

      You may treat Covered Source licensed under CERN-OHL-W as licensed under
      CERN-OHL-S if and only if all Available Components referenced in the
      Covered Source comply with the corresponding definition of Available
      Component for CERN-OHL-S.

  8.4 This Licence shall terminate with immediate effect if You fail to comply
      with any of its terms and conditions.

  8.5 However, if You cease all breaches of this Licence, then Your Licence
      from any Licensor is reinstated unless such Licensor has terminated this
      Licence by giving You, while You remain in breach, a notice specifying
      the breach and requiring You to cure it within 30 days, and You have
      failed to come into compliance in all material respects by the end of
      the 30 day period. Should You repeat the breach after receipt of a cure
      notice and subsequent reinstatement, this Licence will terminate
      immediately and permanently. Section 6 shall continue to apply after any
      termination.

  8.6 This Licence shall not be enforceable except by a Licensor acting as
       such, and third party beneficiary rights are specifically excluded.
