I work with a company that has a software development subsidiary. They have developed a customised drawing and estimating package that runs on the back of Autocad ™. .
My questions are:-
1) Is there an existing emulator that could do this or
2) If there isn't could they develop their own emulator using that stuff you call "source code¨
3) Is there a better approach than either of the above


[moved from Software by spinynorman]

You could try in wine/crossover office:

http://appdb.winehq.org/appview.php?iAppId=86

here is what I found for supported versions. Check if this helps, depending on what version of autocad is required for this estimating package.

how about qcad? I've never used it, but I am sure you could save the drawings as .dxf, which Autocad (and any Cad) should be able to open.