Add documents with policies and some rationale for copyright and license in p4lang projects

[jafingerhut]

This is nearly identical to the documents proposed to be added in this PR created early in 2025, which incorporates all changes made responding to comments on that PR that existed as of 2026-May-26 when this PR was created:

• Add document describing the goals and plan of p4c software license tracking p4c#5110

In addition, it adds a new article README-choosing-copyright-holder-and-license-for-new-files.md that I propose we include a link to whenever someone creates a PR that fails the reuse lint CI check, so that the PR creator can have some guidance on what they need to do.

[jafingerhut]

Addendum to previous comment: There may be some comments and suggestions that are still part of this PR: p4lang/p4c#5110

that have not been incorporated into that PR, and therefore also not (yet) into this PR. Linking to that one for future reference to all comments on that PR, in case they are useful.

[jafingerhut]

This PR's changes are based upon those in PR #9. That other PR should ideally be approved and merged before this one is merged.

[jafingerhut]

@fruffy Thanks for the review and approval. Given the wide scope of these articles applying across all p4lang repositories, I will wait a bit longer for at least one or two others to have a chance to review and ideally approve it, too, before merging. Of course I expect we will make updates and corrections as needed over time, but great if a few minds spend some time thinking about this before merging version one.

[fruffy]

@fruffy Thanks for the review and approval. Given the wide scope of these articles applying across all p4lang repositories, I will wait a bit longer for at least one or two others to have a chance to review and ideally approve it, too, before merging. Of course I expect we will make updates and corrections as needed over time, but great if a few minds spend some time thinking about this before merging version one.

I would consider tagging the same people that were involved in the discussion here: p4lang/p4c#5110

[jafingerhut]

@Dscano @vlstill @asl @ChrisDodd @kfcripps @pkotikal @thomascalvert-xlnx @vgurevich @AlexeyAliev This PR in the new p4lang/.github repository is nearly identical to one I created in the p4c repository in early 2025, here:

• Add document describing the goals and plan of p4c software license tracking p4c#5110

but then I let it sit idle for many months before returning to focus my time on it.

I decided to close that PR on the p4c repo, and open a similar one in this repo, because repositories with names of the form https://github.com/<github-organization-name>/.github are an explicit feature created by Github that enables files in such a repo to be "global" to the entire Github organization and all of its repositories.

Most of the files in this PR are identical to the latest commit of the earlier p4c PR linked above. However, there are several threads of comments and discussion on that older PR that may not have been resolved to the commenter's satisfaction. Please refer to the comments on the p4c PR to refresh your memory what those comments are.

In the past month or so I have added SPDX-License-Identifier comment lines in all files of the p4lang repositories in "group 1" below. The "group 2" repositories are only partially done (still a work in progress):

• behavioral-model p4-constraints p4-spec p4mlir-incubator p4runtime-shell pna ptf tutorials (group 1)
• .github PI open-p4studio p4-dpdk-target p4app-TCP-INT p4app-switchML p4c p4runtime tdi (group 2)

To the repositories in "group 1" I have also added a new CI pre-commit check such that if a PR adds new files without a syntactically correct license annotation, or is missing a copyright notice, the pre-commit check will fail. My hope is to include in the failure message of this CI pre-commit check a link to an article that guides the PR submitter on what they need to do in order to correct the issue.

Thus new in this PR is a file named README-choosing-copyright-holder-and-license-for-new-files.md that I hope becomes the article we link to in such error messages.

Comments/suggestions/corrections/questions are welcome on any or all of this. I don't think we need unanimous approval from all of you to merge this as "version one" of the p4lang repository guidance and policies on copyright and license annotations, but it would be great if at least a few more people could read this, think about it, and provide your feedback, before we merge "version one".

I plan to review all of this with an intellectual property specialist at the Linux Foundation soon-ish, too, but I don't think that is necessary for merging "version one". If you would prefer that we wait and merge it until after approval by such a specialist, let me know.