OpenJournal offers cloud storage for journals. It required an account creation and it is currently in open beta, ie. the data are backup twice a day, but the server can undergo unplanned maintenance.
Accounts creation is done by filling the registration form. A Token will be sent to verify the registration email. Then the user can connect to its remote journal.
Go to File -> Cloud connection.
Enter username and password.
Concurrency is not supported in OpenJournal. You can’t edit the same journal on several computers. However, one journal open on several computers will update itself if the two subsequent changes on two different computers are separated by more than twenty seconds.