Changing text on the buddypress registration page

I keep getting hammered by idiot spammers who are finding my website through the search term "yes i d like to create a new blog". Another term they are using is: "registering for this site is easy,"

Both phrases are on the registration page http://teatra.de/register and they seem to be coming in droves. Those terms are being used to find my site every day. This is, of course, because those terms are default in a WPMU/BP setup. I want to rewrite these terms to something more specific to my niche and with the hope that in time I'll stop coming up in the Google search results for it.

Where in the code do I need to look to find where this page and those phrases are generated? I'm not familiar yet with the file hierarchy to go digging around for days and days to do this, does anyone know where this is found?