AutoCADder

Autodesk has recently taken two interesting legal steps trying to protect their IP (and business...). And it seems that both steps can be quite successful.

1) The license agreement for the ObjectARX library (a component for software developers neccessary to make ARX applications for the AutoCAD product family) now explicitly excludes using ObjectARX for developing add-on applications for AutoCAD LT (and DWG TrueView). This is what most LT application developers has done before. Now (AutoCAD LT 2007 and on) Autodesk can lead legal actions against such developers. This will probably mean the end of larger add-on applications for AutoCAD LT.
See ObjectARX license

2) Autodesk has applied for a trade mark on the "DWG" name (AutoCAD drawing file extension). Evan Yares (OpenDWG/Open Design Alliance) reports on this step (I don't share his often paranoic insights of the Autodesk world). Trademarking DWG will probably make end (or tougher life) to the "would-be" DWG-compatible applications and libraries trying to reverse-engineer the Autodesk proprietary DWG file format.
See Autodesk trademarks