Is it possible for Dropbox to synchronize files and folder labels?
I mean, if I label a folder in Dropbox folder, it's automatically labeled on all other computers?
My DOpus is currently set to store labels in NTFS.
Can Dropbox sync NTFS ADS metadata? As far as I know it can't, but I may be wrong.
Storing the labels as paths in your config is the other option, and then requires synching the relevant config files in some way.
You'll also need to sync or copy the config files which define what the possible labels are.
Apparently, syncing ADS is not possible.
If I decided to sync label config file on my own, I guess I would have to exit DOpus completely before replacing the config file?
Correct. With that particular config file, Opus won't notice changes made once it is already running.
From a quick test, you can usually replace it and then restart Opus, as long as Opus wasn't about to write out a new version of it due to label changes. (No guarantee it will always work that way in the future, though.)