I would probably be most upset if a program had its license changed to be "permissive" like the Expat License. I might accept making a reasonable number of contracts to provide a "proprietary" license that doesn't give any new person (or corporation) permission to distribute software, but a "permissive" license allows people to work against the Free Software Movement without any oversight.

That being said, I don't think I would be satisfied if a contract specified that "an OSI license" will be used: I would prefer for a specific license to be used rather than just one of a class of licenses. However, if an appropriate license is already being used, I wouldn't have to sign anything to protect myself!

In general, I'm probably against changing the license of any software: changing a license seems like a lot of work that can probably be better spent elsewhere, and I consider it to be unlikely that any GPL license will need to have a new version anytime soon (they might, and the v3 versions are clearly better to use than any preexisting version, but they might also change for the worse if the FSF changes for the worse), and the GNU AGPLv3 clearly reflects the present state of the art of licensing (so using any other license that is compatible with it would strike me as strange). If I actually had a reason to study any source code that wasn't available with the GNU AGPLv3 or the GNU GPLv3, I would probably be better off studying the requirements of people who use that software and making my own version with a license I prefer: that way I'd provide more certainty that my changes are available with an appropriate license.

Changing the license of existing projects is clearly useful sometimes, but adapting proprietary programs for use with more open systems hasn't been very useful to me so far. For example, I use LibreOffice rather than trying to get Microsoft Word to work with my computer.

There might be some people who argue that any influence of a GPL license will make their business model less profitable, but if that's the case we're already dealing with business, so I might as well receive my fair share of money and influence from the business (or withhold my participation entirely, if that would be less harmful).

Just to be clear, I'd avoid studying source code only available with the GNU Lesser GPL unless things change.

FYI, I’m discussing "studying" instead of "changing", since avoiding even looking at source code of questionable provenance might help protect me from accusations of plagiarism. If someone exploits a computer system to copy source code without permission and shares it with me, and then I make a similar program, the copyright holders whose program I copied might have a justified reason to complain. However, there is less chance of that if I study people's public messages or even compare the behavior of one program to another, and if I don't study a program, I probably can’t change it either.

I'll note that, despite what I've written,

• I don't actually scrutinize licenses of repositories very much: if I come up with a useful patch, I'm inclined to share it even if it's unclear what license will be used with it. However, I do scrutinize the license of programs I install (for example, I like that yast2 lets you see the license of packages before installing them), so I'm more likely to want to contribute to programs that are compatible with a GPL license.
• I have submitted a patch with text like "By submitting this I give permission to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of this contribution to any person obtaining a copy of this software" that was provided as a template.
• I wouldn't complain much if someone got paid $1,000,000 to distribute some software with the Expat License, since I can't fault them for taking care of themselves.

FYI, "nominal consideration" is very likely sufficient to establish a contract ("contracts in the United States have sometimes have had one party pass nominal amounts of consideration, typically citing $1"), and a contract is probably hard to neutralize in general due to things like mutual drafting clauses and savings clauses.