WordPress founder Matt Mullenweg and Chris Pearson of DIY themes are currently having war of words over Twitter. Matt is unhappy that unlike other premium themes, Thesis doesn't distribute/sell under GPL licensing system.
Matt called out "developers of "premium" themes as "evil" that're not released under GPL. WordPress itself is released under GPLv2, and Mullenweg feels that products developed on top of WordPress need to be GPL as well."
"To Mullenweg, if you build off of free software, and depend on it, to license them under other means is a breach of ethics." Matt even stated, Thesis doesn't work if you remove WordPress, so it shouldn't be classified as its own product for licensing. And, Matt isn't wrong here, because Thesis extensively uses a lot of code from WordPress core.
Andrew Warner of Mixergy, attempted to play the role of mediator, offering choices to both sides. In the end, the two parties have neither agreed, nor agreed to disagree. Technosailor reports that "this entire argument has apparently spawned due to a security breech in the Thesis code."