A vote for firebird here
Compliance to HTML standards and not to poorly written code is my favourite thing about it (along with teh tabs/auto popup killing)
Yea, I also highly doubt that firebird will be a non-free browser in the future because it's released under a public license. Even if it becomes commercial software (not likely), anyone can jsut take the code from previous releases (or even cvs if lucky) and rebuild the software under a different name.