- MIT: minimal, sweet and very permissive, do what the fuck you want, only more politically correct.
- AL 2.0: BSD only better because more generic and including patent termination.
- MPL: weak copyleft (or weak viral), way clearer than LGPL and still has a strong supporting community.
- GPL 3.0: strong copyleft (or stong viral) because there is no other choice.
- AGPL 3.0: strong copyleft, even hosted.
I would even go as far as arguing that most people who like GPL 2.0 and dislike GPL 3.0 (like Linus) should really be looking at MPL instead.
License proliferation makes the use of any open source software harder. It’s hurting open source because anytime a package is used you have to figure out what the license is and play the compatibility game. Is it compatible with my license? Will it “pollute” it? With just 5 licenses it’s already is a bit of a headache, manageable but sometimes painful. With too many licenses, some more documented than others, it gets close to impossible to release something sane. So choose well and think of your users.
Considering which license to use when you start a new project is really important. It determines where and how your software can be used, how freely and with which restrictions. It’s a balance between protecting your code and maintaining you ownership on one side and making it available with as few strings attached as possible on the other. You can’t achieve both so you have to think of where exactly you stand. Don’t just use the license du jour because that’s what everybody does, all licenses haven’t been created equal and some of them are really clunky.
As a result of your choice, some people who would like to use your software won’t be able to (like Apache if you choose GPL). Is that a problem? As a result of your choice, some people you may not want to give your software for free to, will use it for free (some BigCos if you use MIT or AL 2.0). Is that a problem?
Open source is all about freedom, the one you keep for yourself, the one you give to others, as a gift. Licenses are at the core of this freedom. Pick one carefully.