yeah nice palette approach, played with it some, and one suggestion would be a darker grey so it has more flexibility in darker scenes, and would essentially become a dark end of the ramp for every colour
and my 2 cents about the licensing, there is already a saturation of tools available and some free, to stand out make sure you implement some features that the others lack, and if you do have competent animation then yeah especially compared to pro motions licensing and prices it'll definitely be worth and very attractive between $10-30
I think $10 will be more attractive generally and you'll have more purchases from people who think 20 might be a tad too much,
at least until you fully implement some of the heavier features, and then as an early adopter's incentive it seems like a good idea to specify how much it will be when you go 1.0 and of course early adopter's should get all updates included, and my suggestion would be to have a Donate button on your site there is goodwill and gratitude around for projects such as these, and the ease of a donation feature may well sway them to throw a few dollars your way =) and the possibility of them feeling guilty for paying so little for it may sway them too
and yeah having a don't release any imagery made with this software will likely be ignored by a lot of people and potentially turn off the genuine so I'd personally not recommend that approach, free ed and Pro ed sounds like a win-win situation, especially if the user loves the interface and gets to the point they start craving the additional features