HTSQL is a comprehensive navigational query language for relational databases. HTSQL is designed for data analysts and other *accidental programmers* who have complex business inquiries to solve and need a productive tool to write and share database queries. HTSQL is *free and open source* software. For more detail, visit http://htsql.org/. This is a source repository for HTSQL. It contains the source of HTSQL core and database backends, documentation, regression tests, and build scripts. HTSQL is copyright by Prometheus Research, LLC. HTSQL is written by Clark C. Evans <email@example.com> and Kirill Simonov <firstname.lastname@example.org>. Generous support for HTSQL was provided by the Simons Foundation. This material is also based upon work supported by the National Science Foundation under Grant #0944460.