I have used FolderSync in the past to synchronize other files between two macs.
http://www.softobe.com/products/flsy/pp.html

I have sync'd over the file :
~/Library/Application Support/OmniFocus/OmniFocus.ofocus

I will post if I have any problems. I have used MS's FolderShare in the past. I am not sold on it, but it is free and maybe helpful in this issue.