A few people have mentioned Space Engineers. I had a quick look before, and it looked interesting, but I really didn\'t want to dilute the free time I have between two games. But enough people have mentioned it now (and I\'m a bit depressed at the thought of having to decipher obfusticate code again) that it might be worth a look.
I just shot off an e-mail to the developers of Space Engineers to see if they are supportive of 3rd party tool developers. I\'m hoping they can do a non-commercial license that lets me develop not-for-profit tools and protects their intellectual property. Or, even better, a NDA program where I can actually get to see their source code. We\'ll see how they respond.
And, in complete fairness, I\'ve also just send a very similar request to Schema. If he is willing to be even a tiny bit cooperative, I can probably do twice as much with SMEdit. We\'ll see how he responds.