Alright, here's what I know at the moment:
First to my own confusion, there are two different packages on the apple.com web page:
1. It's the SDK package, which exclusively contains includes, libraries and manual pages. So, no binaries that one could run. I first blindly tried out this packages. Trying to run my old XDarwin binaries and hope that the libraries would do something, but - of course, without success!
After resignation, I went back to apple.com and found the second package.
Oh, btw, as I realized afterwards by simply looking at the name of the package, I figured that it was just the Sun Java Support...
2. The second one is significantly larger, around 40 something megabyte and it seems to contain the whole thing based on XFree86 4.2.1 (the complete rootless server implementation aswell as the client libraries)
I'm not yet finished with the download. And I won't check it out today -> It's late here, but I think the problem boils down to the fact, that the software is by now not sufficiently documented and Apple does not mark the different packages on their web page well enough.
So, watch out that you get the right package, the second one should contain all the binaries you need.
Good luck and see you tomorrow,
Viktor