ORBit in theory is portable to any UNIX system (using the GNU configure system to define the system). Try it out - it will probably work. However, you may want to see if your platform has definitely been used before
GNU/Linux, i386 Redhat/SuSE/Debian distributions
Solaris 2.6 (UltraSparc)
Digital UNIX 4.0
FreeBSD 2.2.7-RELEASE (Intel)
IRIX 6.2 (you can get it from http://freeware.sgi.com)
If you manage to compile it on any other platforms, let me know.