Over time, I've done several ports of OpenSource software to the BeOS platform.
I got GNU parted to work on several BeOS-based OSes (Haiku,BeOS,ZETA), and got the changes accepted by the maintainer.
I also ported the core of CUPS to Haiku, and fixed several Haiku bugs in the process ;). The modified code for CUPS has not been fed back upstream yet, so up till then it can be found on OSDrawer.