There are three ways to download the latest version of Pololu AVR C/C++ Library:
For Windows users, we recommend first installing Atmel Studio 6.1, then installing the Pololu AVR Development Bundle, which contains the library along with some drivers you might need. The installer for the library will automatically detect Atmel Studio 6.1 and WinAVR and give you the option to integrate the library into either toolchain.
Please see the Pololu AVR Programming Quick Start Guide for detailed instructions on how to get started using the library in Linux, Windows, or Mac.
The source code of the library is also available in the libpololu-avr repository on GitHub.