Ultimately good news, but they're still going to make the expansions proprietary. In any case, after playing a fully open source game like Pathfinder, I really can't go back to buying into the D&D model.
All of the game content is available for free. The only things they limit are some of the flavour text in the splatbooks and of course the adventure paths. All of the mechanical content is fully open. I think that's a pretty good system.
I realise this is a big step forward for them, but it's also the bare minimum they can do to match the standard set by other publishers in the dungeon fantasy space.