A C runtime can more easily be wrapped (eg for Python) and can be used easily with C++ and ObjC. A C++ runtime can be used with C and ObjC, but doing so has significant drawbacks and is not so easy. Using C is the least pain for all the places where it needs to run. I don't have plans to bring back the C++ runtime, as the C runtime can be used just fine in the same applications. The spine-c runtime does not use hacks, it uses features of the C language. 🙂