I'm one of the contributors and from everything I've seen it's not a sell-out situation. The game is GPL so will be remaining open source, the paid-portion of the game will be developed solely by funds from the publisher (I do server stuff so won't be involved in any of that bit.
I'm curious, why isn't the the free version of the game on steam? It'd be a lot easier to get my friends to try it, and setup parties if it used steam friends.