M204 is still alive...
M204 is still quite alive (if not as widely used as once it was); http://www.rocketsoftware.com/products/rocket-m204
(CCA was bought by Rocket Software in 2010; they also bought Sirius Software (the M204 extensions) in 2012)
Given that, unless the developers applied considerable discipline, an M204 database may not trivially map to a relational database, it might be easier just to stick with what's worked. There are likely a few other government users, if one digs a bit, although they may not be the sort to advertise themselves. There's a free and open source clone that runs on Windows called DPT, but it's site has been down for a couple of years now, although a posting to the M204 User's Group Facebook page includes a link to a google drive stash of software and docs; I gather the author had hosting and/or budget issues. :-) It likely wouldn't be suitable anyway (except for training developers), since it lacks some of the security features of M204.