To program (Windows):
1. Download and install Atmel FLIP (http://www.atmel.com/tools/FLIP.aspx)
2. Connect the keyboard, press the program button on the bottom of the PCB
3. Go to device manager, find the atmega32u4 chip and click "update driver" (may be optional; try without first)
4. Open FLIP
5. Device -> Select: choose ATMega32U4
6. Settings -> Communication -> USB, FLIP should show the signature: 58 1E 95 87
7. File -> Load the HEX file you want
8. Click "Run"
9. After programming is done, disconnect and then reconnect the board.