pure-ftpd works on the SL-6000L.
Yes, it will do nothing when run from the console, but that's normal. You should be able to connect to it (you may need to run as root though).
In Linux, you can run *any* command as a background task by appending a space and an ampersand, e.g.:
/usr/sbin/pure-ftpd &
This will run pure-ftpd as a server process. I actually put that line in my /etc/rc.d/rc.local file, since I want to run pure-ftpd all the time.
Downside: if run in the background, the only way to kill pure-ftpd is the standard Unix way:
1) Find the pure-ftpd process via
ps -ef | grep pure-ftpd (*)
2) Look at the first number in the row, this is the PID.
3) Kill the PID number that is associated with the program (kill %pid%, e.g. kill 296 if 296 was the PID for pure-ftpd)
Pure-FTPD uses Linux logins as its account management too. You'll have to use /bin/adduser and /bin/deluser in order to add or delete accounts. *AND* you'll probably want to put passwords on your root and zaurus account (using the passwd account) if you are connecting on any public network.
So there may be better options, but pure-ftpd works. For me at least.
(*) ps: Shows all process on Unix. -e = all process -f = full. grep: searches lines that gets fed into it for a pattern.