SB: some updates
Ram: about 15MB, and that number will slowly grow as the project "N" values increase.
HD: Easily in 5MB
Internet: Any.  Min. xfer/day: about 1kb.  Max. xfer/day: about 1MB, mostly sending.
GUI: Windows only
CLI: Non-Windows only
Overclock Stability: Reports "Mismatched Sums" if overclocked too high, and results become useless.
Cached Units: With SBQueue by Ken Brazier (that's me!)  (
http://home.att.net/~k.brazier/programs/java/sbqueue/)
Sneakernetting: With SBQueue by Ken Brazier  (
http://home.att.net/~k.brazier/programs/java/sbqueue/)
Time to Setup: 10min
Time to complete a work unit: < 1 hour per intermediate progress report; 1 week to 1 month for a work unit.
Can be shut down easily: Yes
Home Page: 
http://www.seventeenorbust.com/
Download: 
http://www.seventeenorbust.com/download/
Program Compatibility: Can run at multiple priorities.  Service installer (included) can set absolute lowest priority ("true idle").
Approx. Team Members: over 300, 20% active.
System Stats: 
http://www.seventeenorbust.com/stats/
TA Stats: 
http://www.tastats.com/sb/
DPAD: some updates
Internet: Any.  Min. xfer/day: 0kb.  Max. xfer/day: megabytes of compressible text.
Proxy Server: possibly FTP (with difficulty)
Firewall: You must be able to connect with active (two-socket) FTP.
GUI: Yes
CLI: Yes
Cached Units: No need - work is not downloaded.
Sneakernetting: Yes, move results.txt
Other Programs Required: DirectX 5 for Windows GUI, None for Windows Command Line, Wine for Linux
Time to Setup: 5min
Time to complete a work unit: minutes to hours
Difficult Install: Select your username by typing it in the user.txt file, as the only line.  To join the TeAm, you must include "[TA]" in your username.
Can be shut down easily: Yes.  Auto-save interval can be chosen in config.txt.  Alt-tab from GUI works.
Program Compatibility: Choose priority normal, low, or idle in config.txt
FAQ: 
http://stephenbrooks.org/muon1/faq.html
Home page: 
http://stephenbrooks.org/muon1/v5.html
Download: 
http://stephenbrooks.org/muon1/v5.html
P.S. Could you explain "Works with Anti-Virus/pop-up blockers"?