They have always said that they will re-evaluate their sync engine support if other well-known sync engines provide the necessary low-level routines for Scrivener to be able to safely sync projects on that engine. As of now, Dropbox is the only one that provides the necessary level of access.
This makes no sense to me. You must be going at this DB thing in the wrong way.
Dropbox runs in the background on your computer. You literally never need to interact with the software directly. It watches a designated folder on your harddrive and syncs whatever you put in there with a remote server.
From the user point of view using Dropbox is no more difficult than using a folder on your computer. Because that is how you use dropbox.
-gr
P.S. You want an alternative to Dropbox because it doesn’t make sense to you. But why is any other sync service going to make more sense to you??