Autodesk has brought an interesting trademark infringement lawsuit against the nonprofit Open Design Alliance (ODA), which could have important implications for people who want to build applications that save files in proprietary file formats.

It seems that AutoDesk has introduced a new wrinkle in the standard AutoCAD .dwg file format, called "TrustedDWG." According to the complaint, "when AutoCAD or another Autodesk (or Autodesk-licensed) product writes and saves a DWG file, the program inserts an identifying watermark and proprietary string of code known as the TrustedDWG." Here's the rub: when AutoCAD opens a .dwg file that lacks the "TrustedDWG" watermark and string, it pops up a warning dialog stating that the file was not created by an app authorized by Autodesk and might therefore result in "stability issues." (Users can disable these warnings, but they are enabled by default.)

In short, Autodesk gets to spread FUD on files created by anything other than "authorized" applications.

Independent developers who make apps that save .dwg files apparently are not terribly happy about having their files treated as second-class citizens in AutoCAD. So ODA created software that allows these developers to create .dwg files that are treated as "trusted" by AutoCAD.

Autodesk then sues, alleging trademark infringement and unfair competition, and the district court issues a temporary restraining order. A further preliminary injunction hearing is apparently scheduled for January 18.

One question: if Google's sales of trademarks as keywords are not a "use in commerce," how is ODA's activity here a "use in commerce" of Autodesk's marks?

UPDATE: The hearing on the preliminary injunction has been reset for February 20. Autodesk's motion papers, filed January 11, are available here. ODA's opposition is due January 29. More info on the case is also available here.