> it's easy to argue that there's no reason for something one contributes under license X to be put under license Y two years later without consent
The problem isn't for the individual contributor, it's the project itself. Let's say for some reason you use Apache 2.0 and then decide you want to add MIT for better compatability with other license. You as the maintainer solicit from all contributors they're approval and you get 99/100, one person holds out and blocks it. What do you do in this case? Go back and remove all their contributions such that you can then continue with the general agreement?
A clause I've been considering, if it doesn't exist somewhere, is to have a majority rules portion to the agreement. But I'm not sure if this works without assigning copyright to the project.
> What do you do in this case? Go back and remove all their contributions such that you can then continue with the general agreement?
Yes, that's what you do, and it's the same in other industries.
For example, when Erlang/OTP contributors were asked to accept re-licensing under Apache2, a couple patches submitted by Netflix's Rick Reed were reverted prior to re-licensing because they didn't sign off.
The license is for all parties, not just to get contributions and then later do with it what you want. If that's how the project is governed, then the license has to reflect that (GPL3 or later) or a CLA must be in place. When that's clear, it's evident to contributors and many will refuse to contribute.
The problem isn't for the individual contributor, it's the project itself. Let's say for some reason you use Apache 2.0 and then decide you want to add MIT for better compatability with other license. You as the maintainer solicit from all contributors they're approval and you get 99/100, one person holds out and blocks it. What do you do in this case? Go back and remove all their contributions such that you can then continue with the general agreement?
A clause I've been considering, if it doesn't exist somewhere, is to have a majority rules portion to the agreement. But I'm not sure if this works without assigning copyright to the project.