Whatever this 1.2 download is, it's corrupted.
It downloads a .bz2 compressed file, and if you extract that you get a .bz2.cpgz file. If you extract that, you get a .bz2 file again.
The only way I can get it to extract is to use BetterZip and extra the package, as the default BOMArchiveHelper app won't do it.
So you get an Opal 1.2 DMG file, which when double clicked notes "no mountable file systems."
This isn't an issue with MacUpdate per se, as the downloads from the developer site (and their mirror) exhibit similar behavior.
Perhaps they should try a better packaging mechanism next time. I've used .bz2 archives before and they've worked (LaunchBar is compressed this way), though frankly straight .dmg files are nicer, and they can compress as well. Maybe not *quite* as well as .bz2, but 2.6 MB versus 5 MB for a download these days is pretty trivial.