AGL2, the successor of AGL, is a game library designed to support the task of developing games in C++. It relies on SDL 1.2.
First, install the dependencies (SDL development files): the base SDL library (the first version, not SDL 2), SDL mixer, SDL ttf, SDL image and SDL net. For the compilation, it might be necessary to install the C++ compiler g++. In Ubuntu 16.04, for example, you can type this:
sudo apt-get install libsdl1.2-dev libsdl-mixer1.2-dev libsdl-ttf2.0-dev libsdl-image1.2-dev libsdl-net1.2-dev g++
Now installing AGL is easy. Just type the following in a terminal (from the src directory):
make install
This will install the library for use and development. If you want to use AGL for development you can type make install_debug instead, to install it with debug symbols.