Hi and thank you for your interest!
An official release is planned for this summer, the full license for PC will be around 150€ for GameStart as you can download
it now. Further options are being investigated such as a releasing a C++ SDK.
Sorry for the delayed answer, things are quite busy around here 
.
I think a Publish-disabled version aka Learning edition might not be such a good idea. Shiva did that and not success from what I can tell.
Unity Free/UDK and the upcoming free Crysis SDK are indeed changing how indie game engine show pricing.
Personally I have no problem to pay 100~150€ for indie/hobbyist license, but for general user, I do believe that no price can beat the free price of Unity/UDK/Crysis free version. Lesson learned from Unity's game-changing move of going free: do think out of box when it comes to indie game engine pricing.
Here's one possible license schema (borrowing some ideas form upcoming delta game engine)
- Free License with Core Engine Open Sourced, Can only publish on Windows platform
That might sounds insane, but that's how a new indie engine can get more PR love, and hence more active users.
And a more open philosophy is not only good for long term but also critical for survival.
- Indie License, Can publish on Windows/OSX/Linux (<150€)
That's the version to compete with Unity Pro 
- Pro License, same as Indie License, but add more platform publish support (iOS/Android/...) (~<500€)
That's for serious game developer/studio who want mobile publish support.
Just my 2c.
I have already thought of opening parts of the source. There are a few issues to be taken care of before that can be done as the underlying framework (which is completely separate from GameStart) is used by several companies. I don't think that is insane but certainly needs careful thinking.
Thank you for your input.
If you were to open source it, I wonder 'how much' of the engine sources should be released while keeping a straight compatibility with the data generated by GameStart Editor ?
I'm thinking about a 'bare bone' version, even if I suspect that it should include almost everything, except the Deferred renderer, maybe, or the multiplatform code ?
So many questions
