Broadly speaking, the scope of the MPL, LGPL, and GPL can be summarized this way: MPL: The copyleft applies to any files containing MPLed code. LGPL: The copyleft applies to any library based on LGPLed code. GPL: The copyleft applies to all software based on GPLed code. However, we would recommend reading the licenses to better understand their scope, and in particular, to understand how the LGPL and GPL define "based on."