That code is used for macromedia flash player. Below it you will see the flash file (.swf) which it uses to play.
I think it was created as an annoyance and used to post on forums, IRC, messengers etc to troll people. But it is detected as Exploit MS05-013, so as it tries to use an exploit it can go in the domain list

It is interesting to note that as long as "on.nimp.org" is left the same, you can use any subdomain and directory that you like. For example mdl.on.nimp.org/Drusepth/ is valid.
This will be added soon, thank you.