GT.M. And since I'm at it, here's the third open source Mumps implementation. This one was once commercial and became free in 2000. So it has quite a few years under its belt and is not some hobby project by some enthusiasts, but is indeed commercially operated (e.g. for licenses on systems other than Linux and OpenVMS). If you read through the description, they've thrown the whole collection of buzzwords at the tool. Ok, for a language that simply maps its database as global variables into the programs, STM is so to speak already built-in. Even if that might be a bit of a cheat.