i don't remember if you was the one who already asked this same question a month ago.
i have still some topics to reply.
anyway you can get such limit by using "event scripts".
by putting something like
[download]
if number of connections for this user (or this file?) is greater than 5, than disconnect
this must be translated with macro commands. you'll find a complete list on rejetto.com/wiki
or you can just search this forum, because i posted a similar script in the last 2 months.