If you will not play by the rules of Wordpress then don't play it. Go ahead and make youself a cms and put on it whichever licence you want. Thesis theme is just using popularity of Wordpress to earn money, taking from community and not giving anything back.
I use WP mostly because its options and usability not because certain theme is out there.
Remember if there is no Wordpress there would no be popular themes like Thesis, and if there is no Thesis there would still be Wordpress and community around it.