Thank you for your feedback, Akien!
We plan to keep the game itself open source but we may change the license or exclude the new levels from it.
Amazing! I really like the idea of commercial open source games. It's still a fairly bold move in the typical "obfuscate everything" approach in commercial games, but there are a few good examples out there in the indie scene. I'm happy to discuss this further anytime if you need advice on licensing, etc.