Below is a build-log on how to build Commander Keen: Keen Dreams (which was recently released on Github) on OS/X using DOSBox and a shareware version found online.
Download and install DOSBox
Create a new folder, this will be your DOSBox mount-point.
Copy all the contents of the directories DISK1/DISK2/DISK3 from tasm5.zip to \TEMP
Install Borland C++ 3:
Copy all the contents to \BORLANDC.
Copy all the source files from Commander Keen to \KEEN.
Fire up DOSBox, mount the mount folder to C.
Put the following paths to PATH:
Go into C:\TEMP and run the installer to install TASM.
Go into directory C:\KEEN\STATIC and run ‘make.bat’
In the directory C:\KEEN and run ‘BC’ to start Borland C++.
To change the Borland directories to the correct path go to: Options > Directories and change the paths to C:\BORLANDC\*.
Compile and run! It creates the binary for me KDREAMS.EXE.
But sadly, when I run the executable it says “Can’t open KDREAMS.MAP!” :-(
It turns out you’ll need to own the game’s actual content before you can run this source code.
Thankfully a shareware version can be downloaded here: keendm.zip. This corresponds with the 1.01S version of the released source code, which is also released here.
Copy the missing files (SHL, MAP, AUD, etc) from the shareware version and play your own compiled Commander Keen!