Is there any open source software similar to AutoCAD? Yes, it is QCad. However, QCad cannot open a DWG file produced by AutoCAD, but can read DXF file. For conversion from DWG to DXF, you can use EveryDWG. Since this conversion software is made for Windows, you need Wine to run it on GNU/Linux.
Fortunately, if you only need to view a DWG file, you can use VariCAD Viewer which is available in DEB and RPM packages. All you need to do is sign up for a free account, then download the freeware. You can try the complete VariCAD tool for 30 days as well.