RDKit

RDKit is a free, open-source toolkit for chemoinformatics, combining chemistry with computer science. It provides functionalities for analyzing molecules, predicting chemical properties, visualizing structures, and preparing data for drug discovery. The library is primarily written in C++ with extensive Python bindings. It maintains a regular release cadence with two major releases per year (typically March/April and September/October) and monthly patch releases, indicating active development and maintenance.