I was reading the Bricsys for Linux forum today and came upon this thread. A user is looking for a DWF viewer running on Linux. Right now, he uses a free DWG viewer from Brava! (a Windows app which opens DXF and DWF as well) installed with Wine (the software layer which allows some Windows apps to work on Linux). Unfortunately, viewing performance is poor.

DWF (Design Web Format) was created by Autodesk in 1995 as a means to distribute and communicate design data for users to view, review and print without the need of having AutoCAD (or other CAD software) installed. Since the data is compressed, the files are smaller and faster to transmit. DWF competes against the ubiquitous PDF. From limited personal experience with the former, DWF files can be smaller than PDF ones.