Finally - I found time to write some code! We can now import OpenSong format songs to the development version of OpenLP2 (as of revision 951)
It will import from straight text files, or from ZIP files containing loads of OpenSong files. Note that, unfortunately, there's something weird about importing files with non-ascii characters in their filenames from zipfiles which I haven't got to the bottom of yet. This causes the importer to die horribly with unicode errors.. so that's next on the list to fix!
Anyway, testers - have at it!