How much of that code is still left? I’d think the bigger problem is that they’d have to get everyone who ever contributed to it not as an Automattic employee to agree to a re-license.
Seeing how Matt has acted in the last couple of days, I wouldn't be surprised if they're just going to yank the license from under the project, and just wait for the lawsuits.
It’s another way of fighting back which could be more or less effective. (Right now I am dreading that I’ll need to change the database my RSS reader users because I can’t really use it commercially or open source the code.)