The below is a little old (while I am posting this we are working on 2.10.3), but it should get people up to speed. If you have fixes for additional issues please open a trac ticket, bonus points for patches.

Sage 2.9.1.1 build notes on FreeBSD 6.2 Release

link bash to /bin, link gtar as /bin/tar, i.e. before the bsd tar in /usr/bin link gmake as /bin/gmake, i.e. before the bsd make in /usr/bin

Build Fixes: