[dspillett]

1. Some projects only really had one maintainer, or a small group, so relicensing is a relatively easy discussion.

2. Some projects have a CLA, so all contributions have the relevant rights transferred before the patches are accepted.

3. Some projects are “open source, not open contribution”, though this wasn't common until recently, effectively making them match point 1.

4. Some relicensing is done without consideration for other contributors, in the hope that no one with skin in the game will notice (or take action if they do), so it won't bite.

5. Sometimes getting the relevant permission after-the-fact, if a CLA was not in place, isn't difficult.