Hello! I'm searching for a good alternative to the program AutoCAD and it has to be Open Source or some other freeware since I don't have enough money to buy a license, still I want to start working in CAD.Do any of you know a good OS CAD-program that is compatible with AutoCAD (uses the same file extensions, like DWG)?

Hello Hennish,
You can try to use KOMPAS-3D LT version. It's freeware version without assy support, only 3D part. But its 2D is very good and you can read DXF and DWG files.
You can download it from http://ascon.net/download.php.
 Also KOMPAS-3D LT include ABC manual, and you can learn it very quicly.Ruse2007-12-19 17:12:29

Unfortunately neither Kompass nor any other Open source CAD software can use (read/write) the full DWG file format (you would probably need not just the extension name but the DWG file format).
The closest software is probably Autodesk Inventor LT (currently free) - see:http://labs.autodesk.com/technologies/inventor_lt/

If You download this product and use it in regions different from USA, Australia, Canada and New Zeland, it will be unduly. See http://labs.autodesk.com/files/201_300/209/file_209.pdf question 5.
 
Also Autocad haven't Czech language interface, support didn't avaible, system requarements is very big (see http://ascon.net/requirements.php)
And main - autocad LT have only time license, it will be works until 1 May 2008...
KOMPAS-3D LT haven't any time limitations....
 
p.s. And Hennish searching for a good alternative to the program AutoCAD....