Any chance of the Linux build still on the horizon? Or will the source compile on Linux as-is? I'd be happy to compile if so, but I unfortunately don't have enough experience to take on porting it myself if it would need more than that.
I see the current problem with the Mac build being no one on the team has a Mac to compile on. If that's the same issue for the Linux build, perhaps since it's free you could just set it up in a VM, and wouldn't need to have another machine at all, nor even need to dual boot. Windows Pro has HyperV or there's VMWare Workstation Player (specifically the Player version, not Workstation), both are free for setting up the VM, too, even something like VirtualBox could work if you're graphics requirements aren't too high. That would at least give you an environment to build in and test that it's working without needing to purchase additional hardware or software licenses.