> Sure there are (for some definition of "most important parts). Take a look at GNUstep for a start.
I was following and trying to use GNUstep 15 years ago, and they were constantly chasing a moving target and were not managing to catch up. (Plus naturally the reimplementation bugs, plus the differences in interpretation of the "spec" which forced the programmer to be very careful and not take shortcuts.)
That's the huge issue when you are trying to reproduce an API which is not under your control by any mean, and is still alive and changing.
I was following and trying to use GNUstep 15 years ago, and they were constantly chasing a moving target and were not managing to catch up. (Plus naturally the reimplementation bugs, plus the differences in interpretation of the "spec" which forced the programmer to be very careful and not take shortcuts.)
That's the huge issue when you are trying to reproduce an API which is not under your control by any mean, and is still alive and changing.