After a lot of frustrated swearing and just a little bit of crying I was able to get the Subversion source control repository working on Mac and hooked right into Xcode, so now I'm all source controll'ed up and can make wild changes without fear of losing everything. Tip: If you're unable to connect to the repository despite following the instructions to a tee, try using a file:// URL instead of the one they suggest. I did that and bam, it worked. I suspect some firewall issue on the Mac was blocking the svn+ssh URL, but to be honest I really don't care at all. Despite the article's assumptions I am far too lazy to run some sort of home network with a server and everything. In fact I'm too lazy to run even one computer -- why do you think I bought a Mac in the first place??
OMG ROFL LOL LOL LOL
Ahem. Sorry, I don't know what came over me there. Anyway, it works and I'm pretty happy with that. All kidding aside, I really like how Apple so cheerfully hands out developer tools with Mac OSX. Your average user doesn't have to ever crack open those folders (and hey, no shame on them for it), but for a would-be hobbyist programmer, the system is effectively as open as my old Commodore 64 ever was. That's awfully nice.
I'm going to noodle around with the physics system for a bit now and then call it a day.