Debian for Hexabus Firmware Development - mysmartgrid/hexabus GitHub Wiki
There is little you need for Hexabus Firmware Development.
Install a Debian 7.6 Minimal system within a virtual machine environment.
Use
apt-get install sudo git gcc-avr binutils-avr avr-libc
to install required packages. The goto Compiling Firmware to learn how to compile the firmware for the Hexabus Plug.