Quote Originally Posted by set135 View Post
This is not strictly true; for example, on my amd64 machine running the main userspace in native 64bit and a 3.3 64bit kernel, I can still run a Mosaic binary from 1998. I have a few legacy applications I still run. This is possible by installing and correctly setting up the required libraries. The kernel does not have a driver ABI, but it *does* try very hard not to break its userspace interface backward compatability (syscalls). This is why even an ancient version of libc5 is still happy to talk to a brand new kernel. Of course, other than supporting 32bit stuff on 64bit machines, distributions do not try to bother with something like this, as their users generally arent interested in retro-computing, and attempting any sort of generic solution would be difficult and involve unknown gobs of archaic libraries.
Yes, that's the key...installing the right libraries. For a techie, that might not be a super hard task, but for an average user, that's beyond their comprehension. They don't even know what libraries are, let alone where to find them and how to install them. I can run programs from the late 90s on Windows without having to go and download special libraries. Microsoft, for better or worse, has even bent Windows over backwards to make sure that it can run the old setup programs without having UAC get in the way.