They can be moved (almost) anywhere you want. I'd recommend that they be in /usr/share/boinc/, but that's a personal preference.
If you're familiar with UNIX/Linux/BSD, then just mkdir /usr/share/boinc, chown it to root:wheel, and then open /usr/share/boinc so that you can drag-n-drop the files in ~/ into the boinc ƒ. Once that's done, you'll have to cd /usr/share/boinc before running the client (BOINC will store files in the current working directory).
If you're using Deep Thought, then you can move the files into ~/Library/"Application Support"/"Boinc Data"/, and Deep Thought takes care of the rest.
Let me know if my instructions are bad (it's 03:30 here and I'm exhausted).