1)They had a public forum, i didn´t know,... http://forum.opendesign.com
Some rooms in this forum are private.
2) In the new version of the website they hide the name of companies
like Esri, Adobe, bentley,...
In the especification they talk about interesting things:
The OpenDWG file format specification, from the Open Design Alliance,
is based upon AutoCAD's undocumented DWG file format. This
specification includes versions from Release 13 up to and including
R2004, and a partial description of the 2007 format.
We strive to make OpenDWG as compatible with AutoCAD DWG as is
possible. However, you will find in this document, certain bit and
byte values listed as "unknown." Although we invest tremendous effort
in reverse-engineering AutoCAD DWG, some of these values have resisted
our efforts. While we are able to read and write DWG files with
excellent AutoCAD compatibility, we continue to work to improve our
understanding of all the data in the DWG file. If you find
information which will help us to understand any unknown values, or
would like to get an update, to see if we have further information on
these values, please contact us at our online support forum,