FreeCAD and DWG Import

Why Can't I Import DWG Files into FreeCAD?
The DWG format is a closed source binary file format that is not directly supported by FreeCAD. It requires an external 3rd party file converter to first convert then import the conversion into FreeCAD for use.

Teigha Converter

 * homepage: http://www.opendesign.com/guestfiles/TeighaFileConverter
 * license: freeware
 * optional, used to enable import and export of DWG files

The Teigha Converter is a small freely available utility that allows to convert between several versions of DWG and DXF files. FreeCAD can use it to offer DWG import and export, by converting DWG files to the DXF format under the hood,then using its standard DXF importer to import the file contents. The restrictions of the DXF importer apply.

Installation
On all platforms, only by installing the appropriate package from http://www.opendesign.com/guestfiles/TeighaFileConverter. After installation, if the utility is not found automatically by FreeCAD, you might need to set the path to the converter executable manually, in the menu Edit -> Preferences -> Draft -> Import/Export options.

DraftSight
There is a free commercial program called Draft Sight (http://www.3ds.com/products-services/draftsight/overview/) that can import most DWG files and can save and export in formats that are friendly to FreeCAD.

Export Your AutoCAD files in Friendly Format
Exporting your AutoCAD files in a more FreeCAD friendly format, like DXF R12 or R14, SVG, and if version supports it, IGES. All are better alternatives to the DWG format when using FreeCAD.

It is important to know that, contrarily to popular belief, there is no difference between the contents of a file saved in DWG or DXF formats, provided it is the same version (ex. DWG 2014 vs. DXF 2014). Both formats are maintained by Autodesk, and they both support exactly the same features. The difference is that DWG is closed (machine-encoded) while DXF is open.

Promote the use of alternative formats
Simply put, stop accepting work done in DWG format. In practice, this is often easier said than done. Still, it would not be bad practice for users and supporters of FreeCAD to avoid and reject the DWG format whenever possible.