I'm glad to hear that it's open source now. I specifically took issue with advertising that it would be open source before the Kickstarter, but then open-sourcing it became a Kickstarter "stretch goal" implying it would have remained closed if that funding goal wasn't reached. I was on board until that surprise.
Looking at the Kickstarter right now:
"Stretch Goal 3: Modding Support
This goal includes three things in specific:
The game source code will be publicly available!
...
The code will be released under a license that prohibits using it for any commercial activities, and requires you to share-alike any modifications you make. The release will also not include any assets, so you'll still need a copy of the official game to play it."
My intention was always to make it available as open source. The stretch goal was there for the rest of the things and to provide some extra incentive.
The license for the code is zlib now, but the assets remain closed. I think that is a fair trade.