We use the VHC (Variable Hilt Components) M29x1 threading system. You can only customize XENOPIXEL and PROFFIE lightsabers. You customize XENOPIXELS by changing the soundfonts and config.txt on the SD card. You can also update the firmware there. 

Our Proffie sabers are based on Arduino and open-source. It can therefore be programmed by YOU. Check this website! 

Check this website too for downloading sound fonts and some guides! HERE