Official comment
Hi Alan,
Unfortunately there is no equivalent of "unlink" on the Mac client. You'll need to do the following so you can change the user logging in on your Mac:
1. Quit Syncplicity: Click on the Syncplicity icon on the menu bar, and then select 'Quit'
2. Drag Syncplicity from the Applications folder to the Trash
3. Drag the file /Users/[USER_ID]/Library/Preferences/com.syncplicity.syncplicity.plist (where [USER_ID] is your account ID) to the Trash
4. Restart your Mac
Hope that helps.