The EPSG has been around for what seems forever and the codes and definitions have made their way into Open Source GeoSpatial and Commercial software.
One difficulty has been the way many packages have implemented the database. Schlumberger converted the tables into CSV files for lookup with their initial implementation, then they adopted Mentor Software's approach and Mentor's C++ libraries. Different people see the data outside of the traditional MS Access approach and most often turn to some database that is not owned by Bill Gates! I think Larry Ellison was happy about this. EPSG realising this, then started releasing the data and data model in many different RDBMS formats (SQL scripts to create the tables and populate the database).
They released Version 6.14 on 2 September 2007.
There are various software providers and oil service companies that have taken the SQL and have produced web-sites that allow users to query the EPSG dataset in many different ways.
Three very useful sites are:
Developed by Petrosys for the oil and gas industry.
Developed by Howard Butler and Christopher Schmidt. They had a very simple aim: "hopes assist others in their understanding, recording, and usage of spatial reference systems". And they are succeeding. The site provides various formats for the codes to implement into web-mapping and software development.
This EPSG viewer was developed by Concept Systems Ltd., division of ION Geophysical Corporation. ION was previously known as Input/Output (I/O) and on September 21, 2007 they changed their name to better represent their services.
Have fun with these sites, and if you have any questions about the EPSG database, do not hesitate to contact me at the Terra ETL Website, under About Us.