Morrus at ENWorld describes it far better than I could, and of course you'll probably have seen this everywhere else as the news is now pouring pretty freely on D&D news.
Pretty cool idea. I think this lowers the chanes of an OGL or SRD at this point, but it sounds like WotC has decided that the real benefit of the OGL (to them) was the online accessibility of the rules for players who couldn't pony up for a rulebook, and that making the core rules free will accommodate that.
It also means that WotC is trying hard, or so it seems, to court the older pro-OSR crowd by offering a full-featured but pared down version of the rules online. The price point is right....free directly competes with and in many cases beats most other OSR games out there.
The question still remains: how will one be able to publish content for 5E? At this point, if they don't offer up an OGL then maybe they can at least announce some very 3PP-friendly licensing agreement, or a tacit acknowledgement that the gaming community likes to publish content for D&D and can do so without worrying about draconian GSLs.