[Proj] Difference between Proj4 datums and EPSG database

[Erich Sadlowski]

Hello all,

using the same epsg number one can get different results for proj4 (e.g. cs2cs) 
and other programms.
For example: When I use 31466 (DHDN, Gauss-Kruger zone 2) a datum "potsdam" ist 
used. This points to "Potsdatum Rauenberg 1950 DHDN". But in the EPSG database 
Potsdam 1995 ist used. Inspecting the "towgs84" parameters you can find great 
differences.

My question is: Why is a different and obsolete definition used in proj4? Why 
aren't the lines in the epsg file corrected to the "offical" EPSG towgs84 
parameters - although in the release notes I can find the statement "Upgraded 
to EPSG 6.11.1 database". 

Many greetings
Erich