This is what I found at the SETI website that should make anyone a little weary of thier intentions:
"SETI@home connects only when transferring data. This occurs once every few days and lasts for about 5 minutes. All of the processing is done off-line."
What does it process off line that can be of any use in the search for ET. Spyware does this, keeps track of key strokes etc.
Are they searching for ET's that live on earth using home computers by recording thier keystrokes?
As for the "firewall" thing, this program too also tells you how to set up a proxy that allows it through your firewall if you have troubles running the program:
"SETI@home uses the HTTP protocol, and work through any semi-transparent firewall that allows outgoing Web traffic. The latest versions of SETI@home should work through more restrictive firewalls and proxies.
If you are having problems connecting from Windows through a SOCKS proxy, you could also look into SocksCap by NEC at
http://www.socks.nec.com/sockscap.html and Hummingbird Socks at
http://www.hummingbird.com/products/nc/socks/index.html Both let you use software as if it were "directly connected to the Internet".
If you're STILL having trouble connecting through an HTTP proxy server and you are running SETI@home on an older version of Windows 95, Microsoft has an updated Winsock 2 driver which corrects the problem, and lets the SETI@home client connect. Search for "Windows Socket 2" in the Product Information section of the Microsoft web site. The file is about 986 kbytes, and post-dates Windows 95 Service Pack 1. "
Another thing that I find odd is that unlike other downloadable programs I can't seem to find anything on thier privacy policy, I typed it in the search under FAQ's and came up with a list of "this page cannot be displayed"?
I don't know but if you read through this stuff it all seems a bit fishy too me

P.S. I might belive some of this about the telescope but a home computer isn't a radio transmitter/reciever so that still doesn't explain what data it is collecting?
And you say it doesn't have permisson to act as server, it doesn't have too now you gave it permission when you installed the program, you allow it to gather information, and you allow it to retrive it, YOU are the server!