don't underestimate the capabilities of `volunteers', or floss developers; nearly 30 years of apple software was thrown away again and again, and apple jumped to something new without much backward compatibility. So, they enabling sophisticated development by paying is a temporary illusion.
Are you referring to the move to OS X? Apple ran the previous operating system within the new operating system just to run those old apps, and Carbon was provided as a transitional API for many years. I'm not sure what this has to do with anything, really.
A backwards compatibility argument (whatever it may be) doesn't make sense here, as Clang has been designed to be backwards compatible with GCC-based projects.
