Apple came back in the late nineties, in part, because they copied and pasted the magic numbers from the Bell System Five codebase, e.g. 1 for exit(), etc. Capitalizing on UNIX popularity helped Apple succeed. So they shouldn't treat Bell Labs technologies like it's their own implementation detail.

For example, Microsoft has the right to break NTDLL because they invented it, and never intended for it to be used directly by app developers. Windows was designed from its beginning to have dynamic system interfaces too. In the UNIX community, DSOs have always been extremely controversial, since they raise legal questions compared to SYSCALL and INT trapping, and they violate the ability of a program to assume complete control of the full virtual address space.

If Apple devs are reading, then please, we love your products, but we don't love DSOs. Please grant us the freedom to choose. Please keep SYSCALL stable. It'd also be great if you didn't add special-cased code to XNU that blocks open source Actually Portable Executables, like you did with UPX. Email me (the author) your feedback instead. I'll do anything to help, short of adopting a second WIN32 linkage model.