Beware GDL adapater in AutoCad!!
We found a bug, and although it was reported to Graphisoft, I don't think it was ever fixed.
The bug... try dragging an object by selecting one of its handles (hotspots, I suppose) without using the AutoCad 'Move' tool. For us that caused AutoCad to hang - and produced corrupt files.
It works fine if you move an object with the 'Move' tool.
AFAIK, if you have other ArchiCad libraries the free downloadable version does not have a limit of only 20 objects, it's just that you get only 20 objects when you download the Adapter.