GEOS (Geometry Engine, Open Source) is a LGPL licensed C++ port of the JTS Topology Suite, used by many free software packages (PostGIS, QGIS, MapServer to name a few) for low-level topological operations.

Initially sponsored by Refractions Research and Vivid Solutions under the technical advice of Martin Davis (JTS designer), GEOS was the engine that would turn PostGIS into a fully compliant OGC spatial database.
Martin wrote his version of the story up to that point here.

In late 2003 I got a consulting contract from Refractions to work (remotely) on setting GEOS straight to a 1.0 level, after a period of struggling with memory leaks making an official release impossible. That's when I met (virtually) Paul Ramsey.

Since then I've continued to work on the codebase with different committment levels.
Notable improvements I worked on, beside the overall maintainance, include: