customizr

Simple and fast WordPress theme designed to help you attract and engage more visitors. Provides a perfect user experience on smartphones. Powers 100k+ active sites around the world. Hundreds of 5-stars reviews received on WordPress.org. Maintained by presscustomizr on GitHub, where it has earned 141 stars from the community.

It's actively developed around customizer, gplv2, open-source, and is a solid reference for anyone building with these tools.