Looks like drawterm leaves stuff in the cut buffer. Go to terminal or Firefox and cut a dozen lines. Go to drawterm and paste. Go back to terminal or Firefox and cut one line. Go back to drawterm and paste and see the new bit overlayed with the old stuff. Looks like someones forgot to check a lenght and is instead reading until it finds a newline. Don't really have any experience with the mac window stuff, but that's what it smells like me.
Look at all those gotos. Must be the FORTRAN version of the email. BC