Using 1Password on Mac OS X 10.4 (Tiger)
While 1Password 3 requires Mac OS X 10.5 (Leopard), 1Password 2 supports Mac OS X 10.4 (Tiger). Tiger users can download 1Password 2 from the main downloads page.
Syncing Tiger with Leopard and Snow Leopard
The data files in 1Password 2 and 1Password 3 are compatible, so you can sync your data between any combination of Tiger, Leopard, and Snow Leopard machines. Simply setup an sync solution like DropBox on all your machines and your 1Password data will automatically stay in sync.