I can't give any particular specifics on this, but I will direct you to Chris' post on the matter
It's only on our website, for the time being. We haven't announced which other platforms will be carrying Tidalis at launch, but today has been... a day of good news on a lot of those fronts. I can't say anything more at the moment, but we'll have official announcements coming out gradually over probably the next month. And yes, given our choice, that whole thing of registering games bought elsewhere on... certain third party websites that have their own keys... is something we'll do our best to make sure happens with Tidalis, too.
GamersGate will probably have the beta up sometime next week, from the sounds of it. For the other partners of ours, the timing will vary, and we haven't gotten confirmation that all of them will carry Tidalis yet at all (but enough of them have confirmed it that hopefully they all will).
Many thanks for your support! You can always wait until it comes out on your platform of choice if you aren't interested in being part of the beta, too -- we really don't mind it one bit. A lot of the publicity for this game is just getting started, and is going to build towards a July official release.
To make it a bit more clear, we currently have an arrangement with Steam for AI War where you can use your AI War key purchased elsewhere to activate the game on Steam as though you had bought it there. We can't make any guarantees, but should Tidalis come to Steam, we'll push to have activation work with it, as well. We'd like to avoid anyone having to buy the same game twice just to have it on the platform of their choice! That said, feel free to wait if you'd like to be sure. There's no hurry; Tidalis will still be there (and better than ever) in a few months.