suggests that OpenBSD 4.4 still fails to build Python if _XOPEN_SOURCE is defined. Henry, can you please confirm that a) the problem still is that select is unavailable if _POSIX_SOURCE is defined, and b) the attached patch fixes the problem (when run through autoconf) The patch is for 2.6, but should be ported to 3.0 also.
Looking at the code again, it might be that definition of _POSIX_SOURCE is not harmful per se anymore, as long as _BSD_SOURCE is also defined. Can you please also try the alternative bsd2.diff?
I tested bsd3.diff on OpenBSD-4.4/py3k and it works fine. ncurses doesn't build and I get a libssl assertion failure in test_ftplib, but without the patch I can't build py3k at all. This is a significant improvement, so +1 for applying the patch.