changing the signup button url in WPMU/Buddypress

you need to look into the sourcecode and find the place where that link is created. I do not know WPMU/Buddypress specifically enough that I can answer this question out of my head, but basically you’ll have the following options:

  • Change the address in the sourcecode – That’s normally the easiest way to do, but you must redo this after every update.
  • Find a hook you can add your own filter function so to change the address on the fly.
  • Or this is a theme issue so you can hack the theme.

Firebug can help a bit to analyze what’s going on, but it’s only in the browser. Changes need to be made on the server side so you should have at least some PHP and WordPress experience.

Or to find a plugin that does the job and you’re lucky. But I’m not aware of such.