This project contains the binary font files served by Google Fonts: http://www.google.com/fonts
The top level directories indicate the license of all files found within them. Subdirectories are named according to the family name of the fonts within.
Each family subdirectory contains the .ttf font files served by Google Fonts, plus a METADATA.json file with metadata for the family, and a DESCRIPTION.en_us.html with a description of the family in US English.
Also /designers contains a list of the Google+ pages for the fonts' designers.
Each font family directory contains the appropriate license file for the fonts in that directory and the fonts files themselves also contain licensing and authorship metadata.
Most of the fonts in the collection use the SIL Open Font License, v1.1. Some fonts use the Apache 2 license. The Ubuntu fonts use the Ubuntu Font License v1.0.
The SIL Open Font License has an option for copyright holders to include a Reserved Font Name requirement, please take care of this important detail.
Source files for each family are often available from the designer, or from https://github.com/googlefonts
These fonts are usually the result of collaborative projects, where you are invited to discuss issues with the designers and even contribute to their on-going development.
When customising or remixing fonts, please do contact the designers to understand what they might need in order to include your improvements.
Most of all: Enjoy the fonts!
– The Google Fonts team, 2015-03-08