Link. Macintouch: “.. SOHO Organizer runs on the iMacs, and the standard Apple Address Book and iCal apps run on Lion and IOS 5 equipment with both sets of apps talking to each other. In other words, you only need to run the SOHO Organizer on the non-iCloud capable machines.
Also SOHO Organizer does not appear to support push notifications. That is, SOHO Organizer syncs on a time schedule rather than immediately after a change has occurred. However, the Lion laptop and the IOS 5 iPhone do communicate with push notifications. I have SOHO Organizer set to sync every 5 minutes, so when it syncs, then iCloud pushes out the change to the Lion laptop and my iPhone very quickly. I am still learning about SOHO Organizer but it seems to do the job.
Others have noted other methods of moving Snow Leopard machines to iCloud. I have not tried it, but for a small group of machines, fruux (https://fruux.com/) might work without having to buy an application. I would be interested if anyone has tried it.”
Not cheap! $100 individual, $180 family. Cheaper than replacing a machine though. Works on 10.5.8