This board is a 1W CATS transmitter, designed to sit on top of a Raspberry Pi. It's fairly dumb - the RF4463 transceiver is connected directly to the Pi via SPI. A few passive components are used for line filtering, as well as to provide a TX LED.
Since the board is so simple, there's no reason it couldn't be used for other projects. It's essentially an Si4463 HAT for a Raspberry Pi.