LGPL switch

[IAlibay]

As per https://www.mdanalysis.org/2023/09/22/licensing-update/#detailing-our-proposed-relicensing-process

We are now at step 3, where we package under LGPLv3+ until we remove our apache dependencies.

Changes made in this Pull Request:

• Update LICENSE files (LGPLv3+)
• Update all code references of GPLv2+ to LGPLv2.1+

PR Checklist

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

Developers certificate of origin

• I certify that this contribution is covered by the LGPLv2.1+ license as defined in our LICENSE and adheres to the Developer Certificate of Origin.

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📚 Documentation preview 📚: https://mdanalysis--4794.org.readthedocs.build/en/4794/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.64%. Comparing base (b254921) to head (ffe8371).
Report is 52 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4794      +/-   ##
===========================================
- Coverage    93.66%   93.64%   -0.03%     
===========================================
  Files          177      189      +12     
  Lines        21742    22808    +1066     
  Branches      3055     3055              
===========================================
+ Hits         20365    21358     +993     
- Misses         930     1003      +73     
  Partials       447      447              

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[orbeckst]

• source code: LGPLv2.1+
• overall package: LGPLv3+ (for now)

Main question: Do we need to include the text of GPLv3 because LGPLv3 incorporates it?

[IAlibay]

Thanks @orbeckst I just added the text because "why not" and centered the LGPLv3 header.

[RMeli]

Just one thing, otherwise LGTM. Thanks for the massive effort!

[orbeckst]

@MDAnalysis/coredevs the license change has been approved by final vote and we will merge this PR in order to switch the license of MDAnalysis to LGPL (as detailed above).

Thank you everyone for their support in this 3-year long process.