The Latency Tester firmware uses the CooCox CoIDE for development along with the gcc-arm-embedded toolchain. The ST-Link/V2 is the cheapest way to load firmware onto a Latency Tester board, though any SWD compatible programmer should work. You can follow these steps to set up a build environment and load firmware onto the board.
Looks like Apache license for the firmware.
Make a robot friend with Adafruit’s CRICKIT – A Creative Robotics & Interactive Construction Kit. It’s an add-on to our popular Circuit Playground Express, FEATHER and other platforms to make and program robots with CircuitPython, MakeCode, and Arduino. Start controlling motors, servos, solenoids. You also get signal pins, capacitive touch sensors, a NeoPixel driver and amplified speaker output. It complements & extends your boards so you can still use all the goodies on the microcontroller, now you have a robotics playground as well.