The whole project is open-source - with complete source code available on GitHub: https://github.com/klokantech/epsg.io Contribution from the online community is very welcome. New features, fixes of bugs and additional functionality can be easily developed by anybody who is interested in improvement of the system...
EPSG.io: Coordinate systems worldwide (EPSG/ESRI), preview location on a map, get transformation, WKT, OGC GML, Proj.4. https://EPSG.io/ made by @klokantech