See the download section to get it. You'll need to re-fetch the svr4.tar.gz source module if you have an earlier version of the emulator already installed. The distribution is broken into three parts. Includes a dozen or so .h files which are needed by the streams driver. SCO and Sun both give their x86 versions away for free for educational or private individual use, so it shouldn't be all that difficult to come across them.
Developers are extremely welcome, and actively encouraged.
Eventually this distribution will get rolled into the -current CVS repository. I'm told that 2.6 executables used to fail utterly with Bus Error signals shortly after startup. Sun changed the syscall conventions used by Solaris between 2.5.1 and 2.6. That's the most recent bit of work I've done on it, so it's the bit that has had the least amount of testing. I've done something a bit dumb by making my code diverge from Christos', and to repent I really should fold my differences back into the NetBSD codebase.