Anyone intimate with the GPL?

[jaguar]

As part of moving back to Australia (don't ask how this works, it's complex) I'm part of a team starting a new website. (no, not jagneedsmoneytochangecareertrack.com). We're looking at useing an existing GLP'd piece of software and intergrating it into what we are writing.

Do we have to therefore release what we're writing? The modifications? How does it work with this kind of customisation of web software? The site would only be used internally and not redistributed as a package or anything.

I guess I'm happy enough to have to code on display if we must, the only downside is the embarassment at the ugly hacked-up bits being on public display.