Nader wrote:does it's possible to combine USBaspLoader with the SD card bootloader togther
Yes, absolutely! To be honest though I don't think this the best way of going about it.
Arduino UNO replaced the FDTI chip with a ATmega8U2 (similar to the ATMega328p but not as powerful) and programmed it with firmware to emulate the FTDI chip. If you look at the UNO board you'll see there's even a separate ICSP connector for hooking a programmer directly to this chip and reprogramming it with whatever you like, it's very easy to turn a UNO into a keyboard or joystick or any other HID device by uploading new firmware.
Gamebuino, as you know, stuck with the FTDI chip. Adding that functionality to the bootloader wouldn't be too difficult, I have a few Freetronic LeoSticks at home based on the Leonardo which I believe do just that. Doing so, however, would require increasing the size of the Gamebuino bootloader to 4k, at which point you won't be able to run any games that are memory-intensive to begin with. You could of course upgrade to a more powerful ATMega chip, although that could cause other compatibility issues.
If you're having trouble sourcing FTDI's then my advice would be to simply replace it with an ATmega8U2 (or even the ATmega328p) and program it with the USB-Serial firmware which you can find in \arduino-1.0.5\hardware\arduino\firmwares\atmegaxxu2. As an absolute last resort you could also use a standard RS-232C cable and interface to it with discrete components as shown in the schematic for the single-sided Arduino board at
http://arduino.cc/en/Main/ArduinoBoardS ... ngleSided3, I've used this circuit myself in the past and it works fine.