The shield is designed for 'classic' Arduinos such as the Uno, Duemilanove, Diecimilla, etc. It uses the I2C pins at Analog 4 and Analog 5. It will also work perfectly with Arduino Mega R3's which have the extra SDA/SCL I2C pins broken out. Earlier Mega's have the I2C pins in a different location and will require you to solder two wires from the I2C pins on the shield and plug them into the different I2C locations at Digital 20 & 21. This shield will not fit easily on top of an Arduino Ethernet because of the Ethernet jack height.
This product comes as a kit! Included is a high quality, USA-made PCB and all the components (buttons, header etc). This product comes with a 16x2 RGB negative. Assembly is easy, even if you've never soldered before and the kit can be completed in 30 minutes.
Comes with a 16x2 RGB backlight LCD, negative display
Plug and play with any Arduino 'classic' - UNO, duemilanove, diecimilla, etc as well as Arduino Mega R3
Uses only the I2C pins - Analog 4 & 5 on classic Arduinos, Digital 20 and 21 on Arduino Mega R3
This board/chip uses I2C 7-bit address 0x20
You can find a great tutorial over at Adafruit - RGB Shield Guide