Syncing Aperture between Macs

RSync the library from the one system to the other when you're at home. It's network efficient, only transfers updated files, and is designed with exactly this sort of thing in mind. It's also free, and installed by default on OSX. It's a command-line tool, as long as you're happy with that sort of thing. It'll keep the libraries in sync quite happily, and syncs both ways.

You'll want something like:

rsync -avh --progress --delete /path/to/source /path/to/target

Depends on whether you mount the remote drive locally, or use an rsync daemon.

Nice instructions here: Software to synchronize two directories (local/remote)

Another possibilty is to keep your aperture library on an external disk. You move the disk from computer to computer. This avoids the sync problem, as well as the possibility that you overwrite new edits with older versions if you forget which one is the most current.

Note that USB 2 is probably too slow to work with. Firewire 2 is probably acceptable. USB 3, thunderbolt, or esata will depend on the capabilities of your macs, but you can get enclosures that support multiple kinds of connections.