It's written in Arc, which is written in Racket... you might find yourself coming up against the limitations of tools which were designed by academics, for academics and never meant to be used in a production site.

Plus I'm sure I've seen pg say somewhere it runs reasonably well now, and when it starts going they flick the switch and bring it back up.

Does the racket-lang website have to be restarted every so often?

Racket is open source. Have at it. http://racket-lang.org

Based on the last time I touched it, I suspect it's a managed memory leak, though. The vast majority of Racket is in racket/base or mzscheme.