At one point, a couple binary loaders were written for C# and java, the latter what is probably used in the internal editor. Someone ported the C# version to C++, but then realized that the Git Repo needed ANSI-C (which in turn needs a lot of scaffolding).
You can track the active development of both the editor and the runtimes using the Trello task boards:
https://trello.com/b/dle5mTBW/spine-runtimes
https://trello.com/b/frGlgsF7/spine-editor
