[duped]

The point I'm making is that its OS vendors job to develop one platform, not software that works on multiple. It seems like you misunderstand that. They don't have a moral obligation to develop APIs that work for other platforms - that's absurd. That's not even what POSIX is, and like I said, POSIX doesn't even cut it for these applications.

The obligation is in the developers making cross platform layers, like GUI toolkits. There's no obligation for MS and Apple to agree on an API, but there is an obligation for the software claiming to target both to support both APIs. That's the very nature of making something cross platform!