DWG is a bit like the DOC format for Word. It started out as the native (ie proprietary) format for AutoCAD. Autodesk created DXF (Drawing eXchange Format) as the public (dumbed down, feature limited) version. (DWG is to DXF as DOC is to RTF - sort of.)
As AutoCAD became established as the defacto standard for CAD software no one using other programs wanted to be stuck in the DXF ghetto and thus the ODA was established. As I recall Bentley was one of the main supporters back then.
In any case DWG is still the native, proprietary format of AutoCAD and thus the ongoing disputes. The underlying issue is over who owns the format, the publisher or the users.
Of course now we have the public DWF format which Autodesk was delusional enough to think could replace PDF in the wider world od e-documents. It remains to be seen if this has any legs even in our world but the 3D DWF seems grossly under-supported for its potential. It is far more useful than the 3D PDF format. I suspect that most vendors are in no hurry to add value to this Autodesk venture.
