Proposed license change to Apache-2.0

[janfb]

Dear SBI contributors,

After extensive discussions, we, the initial copyright-holders of the sbi repository (Jan, Michael, Álvaro, Jan-Matthis, Conor, and Jakob), propose to relicense the sbi library under the Apache 2.0 license. Below, we provide the background and rationale for this change.

Proposed change

Up until now, the sbi repository was licensed under the AGPLv3 license which has a strong copyleft. We suggest changing the license to the Apache 2.0 license. The Apache 2.0 license is a permissive license, (like MIT or BSD3) and is also used in several other open-source projects such as PyMC or ArviZ.

Why do we want to change the license?

Many former sbi contributors have moved on from academia and into industry, but the strong copyleft of the AGPLv3 license restricts the use of the sbi toolbox in their new job: Corporate lawyers usually veto contributions to strong-copylefted code bases to avoid potential litigation. We know our current choice of license limits contributions from sbi users now with private companies and suspect that it might be a deterrent for future ones. After extensive discussions about the implications, we are suggesting to adopt a weak copyleft (‘liberal’ or ‘permissive’) license. We believe that the risk that companies use sbi without giving back to the community is worth the additional community buy-in we expect. We hope that looking at the affiliations of contributors over time will help us understand better this trade-off based on actual data.

Contributor approval for license change

A license change requires the consent of all copyright holders. Each individual who has contributed code to the sbi repository holds the copyright for their specific contribution. As such, we need unanimous agreement from all contributors for the proposed license change (minor amendments, such as typo corrections, do not fall under this rule). Thus, we kindly ask all contributors to express their views on the proposed license change, either by approving this pull request, commenting below that they agree, or by starting a discussion if they have any concerns.

Thank you very much and all the best!
Jan, Michael, Álvaro, Jan-Matthis, Conor, Jakob

[janfb]

Tasks:

• change license comments on top of each file to Apache 2.0
• make sure all files have license comment on top
• update license statements in Readme and Docs
• update changelog with new license

[janfb]

The number of reviewers is limited to 15. Therefore, @jan-matthis @manuelgloeckler @famura @gmoss13 @ppjgoncalves @psteinb @tomMoral @jnsbck @coschroeder @LouisRouillard @bkmi @dgreenberg @rdgao @alvorithm @danielmk @jsvetter @ybernaerts @plcrodrigues @conormdurkan @lappalainenj @jahma @JuliaLinhart @tbmiller-astro @Ziaeemehr @sethaxen @ADelau @ImahnShekhzadeh @VictorSeven @narendramukherjee @MilesCranmer,

if cannot approve above please express your view on the license change by commenting below. Many thanks 🙏

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.03%. Comparing base (4c2f71e) to head (27b308b).
Report is 41 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #997      +/-   ##
==========================================
+ Coverage   76.37%   77.03%   +0.65%     
==========================================
  Files          84       90       +6     
  Lines        6507     6615     +108     
==========================================
+ Hits         4970     5096     +126     
+ Misses       1537     1519      -18     

Flag	Coverage Δ
unittests	77.03% <ø> (+0.65%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
sbi/__version__.py	100.00% <ø> (ø)
sbi/analysis/conditional_density.py	82.53% <ø> (ø)
sbi/analysis/plot.py	71.18% <ø> (ø)
sbi/analysis/sensitivity_analysis.py	18.63% <ø> (ø)
sbi/analysis/tensorboard_output.py	86.58% <ø> (ø)
sbi/diagnostics/sbc.py	95.34% <ø> (ø)
sbi/inference/abc/abc_base.py	26.98% <ø> (+1.17%)	⬆️
sbi/inference/abc/mcabc.py	17.54% <ø> (+1.47%)	⬆️
sbi/inference/abc/smcabc.py	11.92% <ø> (+0.40%)	⬆️
sbi/inference/base.py	92.72% <ø> (+5.63%)	⬆️
... and 52 more

... and 2 files with indirect coverage changes

[jahma]

Yes, I fully approve this change, and believe it would be important to keep the sbi toolbox sustainable!

[psteinb]

This sounds great. I 100% support this.

[gmoss13]

I approve this change, thanks @janfb!

[rdgao]

approved!

[danielmk]

I am in favor of commercially permissive licenses. Personally I use MIT most of the time for my small projects but I fully support the change to Apache-2.0 for sbi.

[ADelau]

approved.

[famura]

Very much in favor of this change 👍

[MilesCranmer]

Approve

[lappalainenj]

approve

[Ziaeemehr]

Approve also.

[JuliaLinhart]

I approve!

[conormdurkan]

Approve

[jan-matthis]

Approve

[ybernaerts]

approved!

[tbmiller-astro]

Happy to approve!

[dgreenberg]

I approve of this

[janfb]

@narendramukherjee @harry-fuyu @VictorSeven @LouisRouillard

[narendramukherjee]

Sounds good to me!

[LouisRouillard]

LGTM!

[milagorecki]

I approve

[VictorSeven]

I think this is a good change, approved

[harry-fuyu]

LGTM! Thank you!

[alvorithm]

While in general I remain a proponent of strong copyleft licenses, I also wholeheartedly share the goal to make sbi (and pyknos) approachable for a wider community of users and developers. Acknowledging compelling arguments made by fellow team members, I am now keen to find out in practice to what extent adopting a weaker copyleft for these projects might help to that end.

Hence, I approve relicensing sbi under the Apache 2.0 license.

[janfb]

The change from AGPLv3 license to Apache v2 license has been approved by all contributors.