Issue 1: On corporations' dealing with GPL
Basically all big companies in the software industry know about the GPL. It's a known quantity. Even if it may not have been publicly enforced, companies have spent lawyers' time finding out the core implications. They know its `spirit', and they mostly equate it with its spirit, i.e. they deal with GPL code according to its spirit. This is true whether they are pro or contra GPL in a particular situation; hardly have big companies ever tried to sneak around it. (Or was there some good enforcement?)
GPL'ing code may not fit everybody's needs but it can make a lot of sense for corporations whose core business is not Wine. Imagine some big hardware vendor (Intel), software vendor (IBM), bank, fortune 500 company, considering the use of Wine for some internal or external product. They don't want to get into the Wine business at all.
It's much easier for them to hire external consultants, Codeweavers, whoever, to implement some stuff for them and give back to the public if they don't run the risk of a) the competition taking the code b) the competition improving it c) the competition getting better products d) the competition not giving anything back Even if the causal connection between the little money you spent and the success of your competition is very weak, you don't want to read that kind of implication in a newspaper. Rather spend 10 times the money and do it closed-up in-house.
Whereas using the GPL, by this time a very well known quantity in most of the above mentioned companies, you can rule out this kind of embarrassment and explain fair and square to your shareholders that a Windows compatibility layer is not a means of competition to you, and that you are just playing by the general rules of the community, and those ensure that your competition will not take advantage of you.
For an enabling technology like Wine that will perhaps never become the one big bread and butter product of a fortune 500 company (sorry Lindows guys), this carries a lot of potential for consultants, both individual and incorporated, whose goal is to offer a Windows compatibility layer and to improve Wine. (1) `We need something like Wine' (2) `We need some enhancements' (3) `We have to give back the source code anyway' (4) `So we can as well outsource that and consult with experts'
In contrast an X11 style license would modify this: (1) `We need something like Wine' (2) `We need some enhancements' (3) `We do not want our competition to know' (4a) `Let's do it in-house', or (4b) `Let's make a contract with our external consultants that disallows them to reuse the code'
Issue 2: On developers discussing licenses
You shouldn't. You can't convince others, and you shouldn't try to. You have the power. Just pick one that fits your goals for yourself and for the project, and move on.
Claus