Curio(u)s question: How does Curio handle syncing between 2 Macs?

a) the Scrivener way via Dropbox, iCloud etc. - i.e., you have to close a Curio file on machine A before opening the file on machine B?
b) the Ulysses way via iCloud - i.e., you can have the file open in 2 instances on 2 machines (maybe even more)

Thanks in advance, Franz