they must go for GPL since it's the beauty of open source. WordPress is GPL software, why the theme is not GPL!?
Chris Pearson adopted split GPL as Matt and WordPress community were creating pressure on him. Chris wanted to use WordPress but he didn't want to adopt GPL. Programming community proved that any theme is derived from WordPress, is subject to GPL too.
then how about the paid premium themes? doesnt that mean everyone must release any of their theme under GPL?
I am not completely versed in GPL, but from what I understand it doesn't mean that the work should be offered for free, it simply says that you can't tell me what to do with it after I purchase it.
I was thinking of buying Thesis theme bet not it is available under GPL great news for the wordpress webmasters...