I emailed them about making an app for Maemo in March this is the reply I received:
Hello James,
Thank you for your interest in Midomi. We do have plans to support the Maemo platform in the future, but it will not be available any time in the immediate future. I am happy to notify you when it is available. Please don't hesitate in contacting me if you have any other questions or concerns.

So good news. @c00l