37E49DF430772F83CE142CBFFE71AEBE65EC7A85 (Duke Nukem 3D Demo .sit file; from MacAddict 13)
The source code for the Build Engine would be released by
Ken Silverman in 2000, followed by a proper release of Duke Nukem's
own source on April 1, 2003.
Although the DOS version does not have symbols to speak of,
the (demos of the) Mac versions do have some in the executable.
Enter DNDEBUG during gameplay, which displays a log of events.
Entering DNRATE also displays the frame rate.
Note that they both display info on the top-left, which may make reading these
at the same time tricky.