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My process of choosing a software license for the project

I'll operate on identifiers from https://spdx.org/licenses/

TL;DR I choose MPL-2.0 if project is not "silly", otherwise I choose BSD-2

If this document is too complex for you, here is a very good primer that I recommend: https://blog.svgames.pl/files/hacktoberfest2017-licences.pdf

DISCLAIMER

The "verdict" is personal opinion that I try to back up with references I find reliable. Also the decisions that lead to final choice don't need to be the same for every project.

Why? You must be aware that primarily it affects the users of your software, then other developers that would like to use your code or binary (e.g. as a dependency) and last but not least potential co-authors that would like to contribute to your codebase. It would be a disappointment if any of them would refrain from using it because of the license.

License choice also has other legal implications, e.g. related to copyrights or patent claims and sometimes even offers additional legal protections to contributors.

The process

  1. I want open source license (obviously) so I need to choose between ones from: https://opensource.org/licenses/alphabetical. Here SPDX table comes handy, so the list can be narrowed further because I want it to be both:

    • FSF approved
    • OSI approved It's also a good moment to distinguish between Copyfree (a.k.a. permissive) and Copyleft:
    • Copyfree (a.k.a. permissive) allows the code to be used in any way
    • Copyleft requires publishing changes under the same license

  2. When I do "silly" project for fun then I choose BSD-2. Linus Torvalds would approve my choice (see [primer]). I prefer BSD-x over MIT because I understand it better (although according to some sources like [A] they are the same from legal point of view).

    • BSD-2 is Copyfree (a.k.a. permissive)
    • BSD-2 is short and understandable for a person that is not fluent in legal language
    • BSD-2 is customizable -> you can have BSD-3 or BSD-4 just by adding one more clause

  3. When I do collaboration project or #1 is no longer considered "silly" then I don't find BSD-x suitable anymore:

    • because of Pieter Hintjens opinion mentioned in [B] (and I don't have another guru in this area that would convince me)
    • because there is some legal controversy around patents when BSD-x is used. I don't understand it but I recognize it based on sources like [C]. This is important from both author and contributor point of view
    • because according to some sources (like [C]) it doesn't give "sense of security and comfort" for the users

  4. Now then, the pretender representing Copyfree (a.k.a. permissive) world is Apache-2.0 - mostly because it's popular (see [D]), backed up by Apache Software Foundation and gives better legal protection (see [C]).

  5. Now, lets pick up pretender from Copyleft world. Copyleft licenses can be divided into "weak" and "strong" (see [E]). I don't want "strong" Copyleft (which effectively takes away GPL family from the pretender list) because:

    • I don't mind that my software can be used as a part of other software that wants to have it's own license
    • "weak" Copyleft gives more freedom to other developers. From legal perspective it gives them more possibilites to use your software

  6. I want license to be recognizable (see [D]). This leaves on the table "weak" Copyleft LGPL family next to Copyfree (a.k.a. permissive) Apache-2.0. But hey, there are more "weak" Copyleft licenses, like:

  7. Based on [F] you can say that LGPL-3.0 didn't cover all usecases for the libzmq project. So it had to be customized (and automatically stopped to be standard license)... Because of this there is MPL-2.0 on their radar.

  8. They say that 7 is a magic number so it's about time to choose between MPL-2.0 and Apache-2.0:

    • I don't want Apache-2.0 because it's not compatible with GPL-2.0 according to [G] (but it's worth mentioning that it's with GPL-3.0, see [H])
    • MPL-2.0 is compatible with GPL familly and also with MIT/BSD-x/Apache-2.0 (see [I])
    • MPL-2.0 "is a simple copyleft license. The MPL's "file-level" copyleft is designed to encourage contributors to share modifications they make to your code, while still allowing them to combine your code with code under other licenses (open or proprietary) with minimal restrictions." (see [I])
    • choosing Copyleft (in general) over Copyfree (a.k.a permissive) is a (sad) lesson learned from the story of "Patrick" described by Pieter Hintjens in [A]

Verdict: I choose MPL-2.0 if project is not silly, otherwise I choose BSD-2. MPL-2.0 seems to be a sweet spot between free software and enterprise world.

Also check

References

  • primer - "Copyleft and Copyfree - a short overview of popular licences" by Artur Iwicki
  • A - Chapter 6, Section "Eat Me" from "ØMQ - The Guide" book by Pieter Hintjens
  • B - Chapter 6, Section "The Importance of Contracts " from "ØMQ - The Guide" book by Pieter Hintjens
  • C - "Open Source Licenses 101: Apache License 2.0" fossa.com blogpost
  • D - "Open source license usage on GitHub.com" from GitHub blog
  • E - "Copyleft" Wikipedia article
  • F - "ØMQ Licensing"
  • G - "Various Licenses and Comments about Them" from gnu.org
  • H - Apache Software Foundation comment on GPL compatibility
  • I - MPL 2.0 FAQ
  • J - "Open Source Software Licenses 101: Mozilla Public License 2.0" fossa.com blogpost