As of today, this project is distributed under a LICENSE that is not an Open-source license as defined by the Open Source Initiative (opensource.org). It is basically a modified Apache 2.0 license that includes a clause (Clause 4.e) that prevents usage in the context of Atlassian products.
That clause was introduced by David Benson (in commit 937537c) after version 4.2.2. He explained his reasons in the commit message and explicitly stated that all versions prior to that commit still fall under the Apache 2.0 license.

This repository is a fork of the archived jgraph/mxgraph library and openly communicates (#1) the interest of forming a community around it. To achieve this goal and catch more interest, there is a need to move back to the standard Apache 2.0 license.

After taking a close look on the repository history, we notice that all the source-code-related commits after the 937537c commit was made by a limited number of contributors (7 contributors listed bellow). Moving back to the Apache 2.0 license is so doable.

Proposal

I think that the best way to make this happen in a non-ambiguous way is to make the transition in two iterations:

1st iteration:

• Add an announcement about the transition process in the REAMDE.md file and explicitly state that any new contribution to this project from now on must be under the terms of the Apache 2.0 license (See Add section about Apache 2.0 license transition to README.md #90 Add Apache 2.0 license note to PR template #91).
• Inform current PR authors about this change and get their explicit acceptance before merging into the main code base.
• Contact all the contributors that pushed source-code after 937537c (listed bellow) and ask them to add an explicit statement at the end of the current LICENSE file as follows:

All contributions to this project made by <PUT YOUR NAME HERE> are published under the terms of the Apache 2.0 license as stated in https://www.apache.org/licenses/LICENSE-2.0.

• In case the contributor is not reachable or for some reasons not willing to change the license, we can think of some possible solutions:
  • Check that the code in question is not already deprecated or re-written.
  • Re-write the non-apache-licensed code.
  • Flag it (i.e. group it in dedicated file/folder) to be used when really needed.
  • Wait until it get deprecated and remove it.

2nd iteration:

• Replace the current license file with the Apache 2.0 license.
• Move the list of authors/contributors to an AUTHORS dedicated file.

List of contributors after v4.2.2

• @mosinnik (1 commit)
   - 469c47b
• David Benson @davidjgraph (4 commits)
   NOTE: Big thanks for his work on this project. Despite the reasons that let him change the license, we hope he can make an exception for those 4 commits that falls under the the Modified-Apache-2.0 license and re-license them under the standard Apache 2.0 license.
   - 5d4f197
   - 82321b3
   - a5ac1ab
   - c85074e
• Dave Morrissey @mcyph
   Majority of the commits after v4.2.2
   NOTE: We cannot ever think about the transition without his explicit approval. We can only hope so !
• Junsik Shim @junsikshim
   Second majority of the commits after v4.2.2
   NOTE: We cannot ever think about the transition without his explicit approval. We can only hope so !
• Gary Kaganas @gkaganas-mparticle @Seebiscuit (1 commit)
   - 07d1b62
• Thomas Bouffard @tbouffard (6 commits)
   - fb7819f
   - 14f5815
   - a2a718b
   - 443ebf7
   - 3a1b08c
   - 760cbd3
• CD Yang @cd-yang (1 commit)
   - 7fa2b43

I noticed that Thomas Bouffard @tbouffard created a branch chore/license_apache2 so maybe he can share with us his opinion.

NOTE: The list do not include the editors of the README.md and documentation related files.
DISCLAIMER: I'm not a lawyer and I have no relation with the Atlassian company in any manner.

Roadmap

1st iteration:

• Add an announcement about the transition process
  • Inform current PR authors about this change
• Get approval about the transition from concerned contributors
  • @davidjgraph Move back to the Apache-2.0 license #89 (comment)
  • @mcyph Move back to the Apache-2.0 license #89 (comment)
  • @junsikshim Move back to the Apache-2.0 license #89 (comment)
  • @tbouffard Move back to the Apache-2.0 license #89 (comment)
  • @mosinnik (Reacted with a thumbs up emoji on Move back to the Apache-2.0 license #89 (comment))
  • @gkaganas-mparticle @Seebiscuit Move back to the Apache-2.0 license #89 (comment)
  • @cd-yang Move back to the Apache-2.0 license #89 (comment)

2nd iteration:

• Replace the current license file with the Apache 2.0 license and remove the warning in README and Pull Request template chore: restore Apache 2.0 license + add a NOTICE file #95
• Add notice about the license in each file. See doc: update copyright and license in source file headers #100
• Update license in package.json files. Done in chore: improve the configuration to build the npm package #87
• Add the list of authors/contributors that re-license their contributions to the NOTICE file. chore: restore Apache 2.0 license + add a NOTICE file #95

Initially planned but need more discussions
We will discuss how/if we handle the contributors list this later

• Move the list of authors/contributors to the NOTICE file.
• Create section dedicated for third-party libraries/projects/code in the NOTICE file.