Yes, that should work. (Or just add that repo, but it's an SDK repo, so better to just grab the .debs you need.)

Oh, and you'd want to get it from here, normally (Diablo ~ Maemo 4.1):
http://repository.maemo.org/pool/mae...free/d/defoma/
But as it happens, it's the same version; that package has not been updated, so it doesn't matter.