non-compete agreement with Gaussian had expired, John Pople joined as both a Director and code developer. In 2000, Q-Chem established a collaboration with Wavefunction Inc., which led to the incorporation of Q-Chem as the ab initio engine in all subsequent versions of the Spartan package. The Q-Chem Board was expanded in March 2003 with the addition of Anna Krylov and Jing Kong. In 2012, John Herbert joined the Board and Fritz Schaefer became a Member Emeritus. In 2018, Evgeny Epifanovsky was named Chief Operations Officer. The following year, Shirin Faraji joined the Board; Peter Gill, who had been President of Q-Chem since 1988, stepped down; and Anna Krylov became the new president. The active Board of Directors currently consists of Faraji, Gill (past-President), Herbert, Krylov (President), and Hilary Pople (John's daughter). Martin Head-Gordon remains a Scientific Advisor to the Board. Currently, there are thousands of Q-Chem licenses in use, and Q-Chem's user base is expanding, as illustrated by citation records for releases 2.0, 3.0, and 4.0, which reached 400 per year in 2016 (see Figure 2). Q-Chem has been used as an engine in high-throughput studies, such as the Harvard Clean Energy Project, in which about 350,000 calculations were performed daily on the IBM World Community Grid. Innovative algorithms and new approaches to electronic structure have been enabling cutting-edge scientific discoveries. This transition, from in-house code to major electronic structure engine, has become possible due to contributions from numerous scientific collaborators; the Q-Chem business model encourages broad developer participation. Q-Chem defines its genre as open-teamware: its source code is open to a large group of developers. In addition, some Q-Chem modules are distributed as open source. Since 1992, over 400 man- (and woman-) years have been devoted to code development. Q-Chem 5.2.2, released in December 2019, consists of 7.5 million lines of code, which includes contributions by more than 300 active developers (current estimate is 312). See Figure 3. Features Q-Chem can perform a number of general quantum chemistry calculations, such as Hartree–Fock, density functional theory (DFT) including time-dependent DFT (TDDFT), Møller–Plesset perturbation theory (MP2), coupled cluster (CC), equation-of-motion coupled-cluster (EOM-CC), configuration interaction (CI), algebraic diagrammatic construction (ADC), and other advanced electronic structure methods. Q-Chem also includes QM/MM functionality. Q-Chem 4.0 and higher releases come with the graphical user interface, IQMol, which includes a hierarchical input generator, a molecular builder, and general visualization capabilities (MOs, densities, molecular vibrations, reaction pathways,