Hi Simone,
Yes, I'm sorry, but you have to be able to run server-side scripts in order to run JSMFeed.pl.
The script will produce a JavaScript file that can THEN be used by client-side-only webmasters, but JSMFeed.pl itself needs to be run on a server.
There are services out there that may let you do something similar on their servers...
Try this:
http://www.feedburner.com
I don't use them personally so can't vouch for them. Others here have used them for converting ATOM to RSS, and found them useful. I don't know if they will also do what you need (only guessing they will).
HTH.
-djr