OpenBabel

OpenBabel is free software, a chemical expert system mainly used for converting chemical file formats. Due to the strong relationship to informatics this program belongs more to the category cheminformatics than to molecular modelling. It is available for Windows, Unix, and Mac OS. It is distributed under the GNU GPL.

The project's stated goal is: "Open Babel is a community-driven scientific project assisting both users and developers as a cross-platform program and library designed to support molecular modeling, chemistry, and many related areas, including interconversion of file formats and data."

History
OpenBabel and JOELib were derived from the OELib Cheminformatics library. In turn, OELib was based on ideas in the original chemistry program Babel and an unreleased object-oriented library called "OBabel."

Major features

 * chemical expert system
 * interconversion of many chemical file formats
 * substructure search (based on SMARTS)
 * fingerprint calculation
 * Python wrapper
 * Perl wrapper