I installed v1r5.1 on on a pretty clean 64bit Ubuntu box and here are my notes:

Install libgtk2.0-0:i386 before you try to install DraftSight. You need this library in order to display the EULA. No EULA = aborted installation. 

sudo apt-get install libgtk2.0-0:i386

Now you can try to install DS

sudo dpkg --install draftSight.deb

The DraftSight installation may still fail because the installation script may depend on some packages yet to be installed.

sudo apt-get install -f

Then you might need libstdc++6:i386 and libglu1-mesa:i386 and the packages they will pull in.

sudo apt-get install libstdc++6:i386 libglu1-mesa:i386

And we're finished. Run it from the terminal window to see if there any libraries still missing.

/opt/dassault-systemes/DraftSight/Linux/DraftSight