Well I just wanted to see what the government was running their websites on, and I was pleasantly surprised.

The site www.whitehouse.gov is running unknown on Linux.
The site www.fbi.gov is running Netscape-Enterprise/4.1 on Linux

and my biggest surprise:

The site www.army.mil is running WebSTAR/4.2 ID/70636 on MacOS

http://www.netcraft.com