XScreenSaver 5.29 out now. The DMG of this version should work again on MacOS 10.6 and 10.7. I had to downgrade to Xcode 5.0.2 to make that work, because Apple are jerks.

I have had two people report, with previous versions, that the auto-updater appeared to run the installer but then didn't actually install anything. If you can reproduce that, please let me know.