LART is a computer similar to the one hidden in TuxScreen. It is just 7.5x10 cm and has no peripherals but lots of pins to connect them to.
Software can be shared between TuxScreen and LART, e.g. original BLOB came from the authors of LART, some kernel development burden can be shared etc.
LART is one of OtherToys.
The same JTAG dongle can be used with both LART and TuxScreen.
Also the same ToolChain can be used with both, and LART authors build good working one from time to time.