Add licenses, make it LGPLv2.1+ contributions going forward

[IAlibay]

This license reconciles long standing issues with the way in which the MDAnalysis package was licensed.

Going forward, until such a time as the codebase is suitably relicensed, the MDAnalysis library will be packaged under the terms of the GPLv3 or any later version.

Any new contributions will be made under the conditions of the LGPLv2.1+.

PR Checklist

• Tests?
• Docs?
• CHANGELOG updated?
• Issue raised/referenced?

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📚 Documentation preview 📚: https://mdanalysis--4219.org.readthedocs.build/en/4219/

[IAlibay]

@MDAnalysis/coredevs I'm going to ask for a PR freeze until we merge this. Once this is merged we then need to make sure that all ongoing PRs agree to license their code under the terms of the LGPLv2.1 and the developer certificate of origin.

[github-actions]

Linter Bot Results:

Hi @IAlibay! Thanks for making this PR. We linted your code and found the following:

There are currently no issues detected! 🎉

[RMeli]

A few quick comments before dosing off. Thanks @IAlibay!

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.01% ⚠️

Comparison is base (ac30c88) 93.62% compared to head (308e33e) 93.62%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4219      +/-   ##
===========================================
- Coverage    93.62%   93.62%   -0.01%     
===========================================
  Files          193      179      -14     
  Lines        25294    24190    -1104     
  Branches      4063     4063              
===========================================
- Hits         23682    22648    -1034     
+ Misses        1096     1026      -70     
  Partials       516      516              

see 14 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
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[lilyminium]

Otherwise LGTM, thanks Irfan.

[IAlibay]

@MDAnalysis/coredevs this is a big operational change, can I please have at least a couple more thumbs up before this gets merged?

[hmacdope]

Looks great @IAlibay, thanks for all your hard work. Very much appreciated.

[orbeckst]

Thanks. Can you please add a CHANGELOG entry, too?

[IAlibay]

Thanks all - @orbeckst can I ask for a quick re-review and then we can go ahead and merge (that's enough approving votes).

[orbeckst]

All good from my end. Thank you!

We do need a blog post as the follow up to https://www.mdanalysis.org/2022/11/07/relicensing in order to explain what we are doing. When we have the URL we can put it into the CHANGELOG retrospectively. But I am not going to hold up the PR for a blog post.

[IAlibay]

Thanks @orbeckst - yeah I just decided to get this done so that we don't accrue any further GPLv2+ contributions. The blog post will be next but might take a bit longer.