*Note I haven't done Linux servers in a while*
From that info I would think you should cd to orangebox folder then run the command from there, so:
cd /home/username/srcds/orangebox
./srcds_run -game gesource +map ge_runway +maxplayers 16
Follow: http://www.srcds.com/db/engine.php?id=1098643920
BUT, use -game orangebox obviously
This is my directory structure on my linux box:
/home/user/Steam/gesource
/home/user/Steam/orangebox
/home/user/Steam/hl2
/home/user/Steam/orangebox/srcds_run
I use this script run from the Steam folder:
cd /home/user/Steam/orangebox
./srcds_run -game ../gesource +ip 192.168.1.7 +map ge_bunker_classic +maxplayers 4