Hi Andrius, 
Thanks a lot for your submission and your interest in GOG. It’s great to see guys like you creating open source games that everyone can enjoy! :) 
We’ve taken a look at zero-k and unfortunately we’re going to have to pass on the game. 
We do release some free games but I’m afraid that zero-k did not really stand out to us and so we feel that it will not be such a good fit for GOG. 
If you have any other games in the future that might be a better fit for GOG, please let us know, and we’ll see if we can work together :) 
All the best, 
Arek Wojasz
Junior Business Development Specialist
www.gog.com