They answered this on their wiki:
> Will KSA be open source?
The game is not expected to be made open source due to certain dependencies that are not also open source. Public code contributions may be opened up in the future pending concerns around effectively managing the potential volume of code contributions.
> The game is not expected to be made open source due to certain dependencies that are not also open source.
That's always kind of struck me as a silly excuse. So just release it without those non-open source dependencies. If there is a community need, they will be re-implemented. There's no law that says an open source release needs to be buildable from day one.