It's called "marlin". The firmware running inside the printer is called "Marlin". Cura is the slicer but does let you upload Marlin into the printers. I don't think the firmware has changed in the last few months. Not sure. I'm very happy with my versions that are of various ages - some more than a year old. Some of the newer Marlin's have features I don't like. So I don't see any reason to rush to upgrade the firmware.
I will wait with the newest Cura till its more use friendly.
Keep it now to Cura 15.04