I've amended the original imgur post to reflect this. You're 100% correct, it's not an actual OS. but rather a primitive GUI of sorts that is an imitation/representation of what I perceive to be an 80s OS.
Yep, so far it's just for QBASIC. I can't see much point in resurrecting it or attempting to port it, but if I ever get into C#/C++/another modern language, I will likely focus on writing new and more interesting apps.