OELib is an open-source small molecule and utility C++ class library, that was at one time the core data handling library for OpenEye. A complete rewrite of these data handling routines was necessitated by fundamental design flaws in OELib. The OEChem Toolkit, a commercial product, is the modern, supported successor to OELib. The decision to step away from open-source was not taken lightly. The open-source version of OELib lives on, distributed on SourceForge, renamed as OpenBABEL.