Mattathias is still under development. If you want regular updates, join the mailing list at
Yahoo groups' Mattathias page. I've recently been added to the development team and we've recently completed an up-to-date design document. The source code is being hosted on SourceForge.net at
this project page.
BTW, why not upgrade to AmosPro v2.0? You can download the latest disk images from
the Amos Factory website. It's in the download area but you have to register on the website to gain access to it.