I think the fact that it is no longer developed nor supported (as was the choice of the devs) speaks volumes. Jeremy is right. There's going to be a lot of schema changes that won't be accounted for.
I suspect devs will tell you not to do it. My advice is the same. However, if you decided to do so at your own risk then the tactic to take is to import into the last version supported by the CLI importer... I thought it was earlier than 1.2.5 to be honest, but if it is that version then import into a clean install of version 1.2.5. If it does work, you can then run a 1.2.5 to 1.4.2 upgrade.