It's a SysV thing, IIRC. It might be an Open Group thing, though. I seem to remember that it was adopted by most of the commercial Unix vendors -- Sun, and SGI I know, possibly IBM and Digital as well.

Regardless, it's just like MSWindows's Program Files, except it works better, because it keeps all files related to that package within a subdirectory of /opt. Personally, I prefer using /usr/local on a real Unix machine, since you almost always have a package system and having a long PATH is a real pain, but developing a package system for the empeg seems like a waste of time, and I can't imagine that there will be many shared files between packages, and I don't think anyone's going to be relying on a PATH on the empeg.

But that's just my 2 cents. It doesn't make a hell of a lot of difference.