What advantage can bring Fort above the storing of all kinds of infos (eg. licences, passwords) in a strongly encrypted zip file (which you can share/keep everywhere) ?

Quiote a lot actually. I agree that an encrypted zip is easy to copy between computers, but...they are not very secure. Cracking password protected zip file is usually very easy. Please, don't keep your important data in a password protected zip file. It's not safe. I've done a lot of security related jobs and auditing and cracked a lot zip passwords.

Also about portability, Fort 4.5 will include features to make it easy to transfer data between machines.