Migrating users from Joomla 1.5 – Using MD5 password encryption?

I am currently in the process of migrating a small community from Joomla 1.5 to WordPress with a Buddypress extension. WordPress is easier to handle and is more suited to our needs. Basically, WordPress ROCKS!

Migrating content is quite easy, however the migration of user passwords is a problem. Joomla uses an MD5 encryption, and WordPress uses a phpass encryption.
A large part of our users have not supplied an email, so it isn’t possible just to send them a new password. The site is an online community for foster children, and some don’t even have an email account. Hence this solution is out of the picture.

I posted about my problems with the only plugin avaiable on the Buddypress forums, but no one has been able to help me. I was hoping someone here would be able to assist me.

I have a couple of ideas as to how i could migrate the user passwords.

– Overriding the phpass encryption and using MD5 encryption instead(i understand MD5 was used in WordPress back in the days?)

– Authorising users with their old Joomla passwords. However when doing that, a weird problem appeared(described in above link). Fixing this problem would probably lead to making everything work.
Any help would be greatly appreciated. Credit on the website, next to a “Thank You” to the WordPress community and developers, is a possibility as a thank you.

I am running the newest installation of WordPress and Budypress. Plugins have been disabled.
Up-to-date PHP and everything else.