If you were to look at the HTTP response headers from this site, you’d see it is being handled by:
Which is a web server you’ve probably never heard of before… Or I should say, you most likely have, but with various different names.
Way back when, this was the Netscape Enterprise Server. Which later became iPlanet Web Server (during the Sun|Netscape alliance). Under Sun alone, it was renamed several times to SunONE Web Server and Sun Java System Web Server (and maybe some other name variants I forget now). Naming nonsense aside, it’s been the same evolving code base all along, best known for high performance and even higher scalability.
Thankfully, Sun open sourced the code in 2009 under the BSD license. Most of it, anyway. Unfortunately a few parts were left out, mainly the administration support, installer and the embedded Java servlet engine. The open source code was kept in sync with the commercial releases until January 2010 (7.0 update 8, using the commercial release version numbering). After that, the open source repository has not seen any activity (not coincidentally, January 2010 was also when Oracle acquired Sun, so this is not surprising).
Surprisingly, the source repository is still available:
hg clone ssh://email@example.com/hg/webstack/webserver
The source as published can be tricky to build and it does not produce an installable package. When I was setting up this site last year I ended up forking this code into http://sourceforge.net/projects/heliod/. The code is the same but I added a rudimentary install script to make it easier to get going. You can download binaries for Solaris (x86) and Linux from the sourceforge page so you don’t have to build it yourself if you prefer not to.