FreeReg
FreeReg is a free software platform to base your own system on
... (and translations of these), guitemplates and a lot more.
FreeReg is currently beeing rebuilt around a REST architecture. A pure Javascript/html client is used as the client (you can ofcourse ad any other client). The serverside is built using Java, and is also currently beeing rebuilt to use a layered architecture, all metadata and data is stored in a database (MariaDb is the default).