On my linux box I run OneSwarm in standard X.
I control it mostly using web remote access, but occasionally I log in with nxserver screen sharing if I want to look at something in the classic GUI. I don't start OneSwarm automatically, but then if my machine reboots I need to log in a enter a pile of passwords anyway so it doesn't bother me that much.
If you want to run it from the command line you should be able to do it with Xvfb, if you have issues with OneSwarm getting killed when you log out you can start it using
screen, that will keep it alive even after you log out.
In general if you want to start something at boot the easiest way is to start it with
cron. On ubuntu you just add it to /etc/crontab with @reboot (remember to specify a username, so you don't run OneSwarm as root) I'm sure
man crontab will tell you how to do it on mandriva.