These are dmd programs from various sources at Bell Labs that can be run as "demos" - that is they can be called by the 32ld program like the other binaries in /usr/dmd/lib. See examples of other binaries in /usr/dmd/lib and the scripts that call them in /usr/dmd/bin and it will be clear how to install them. "postcard" can be placed directly in /usr/dmd/lib/demolib and called directly from a "layers" window.