The vision is to make it available online and offline. It's a little trickier to make it work offline due to how it's being coded for Web, but it will be possible. Essentially, you would still use a web browser like Firefox as the User Interface, but save your entries out into a local folder on your hard drive.
Then if at any time you wanted to migrate to online access, you could upload your entries as a "zip" file using the import option in the Admin Panel. You could do the same with your dictionary database. That way you get the best of both worlds!