Ferenc Bánhidi wrote a patch that allows Pioneers 0.9.23 to build natively under WindowsXP. http://people.inf.elte.hu/banhidi/pioneers/
Note: all client related changes have already been added to the current CVS version.
Keishi Suenaga wrote a patch that allows Pioneers 0.9.33 to build natively under all versions of Windows (Client + Server) pioneers-0.9.33_win_smaller.patch Download binaries + patch
Note: The released versions of Pioneers can run natively under Windows.