the devs made their own game studio and moved on to other projects, nothing about this game is publicized in their discord or on their website so it's safe to assume it's abandonware
I've asked for opensource in discord and no response(probably they will not open it just because there a lot of work done and maybe they will return to it in future).
I've modified a bit Alfa 0.9 version(more enemy for each wave (x2, x3, x4), more time between waves to build more defense and economy, possibly will add some more features like longer storms, more or even endless waves ), I did it just because wanna play more in this game) So if someone wanna - I can share it.