DOSBox is a popular open source emulator of older DOS based PCs. It's capable of playing many of the 'dungeon crawler' CRPGs that you might want to draw maps for within Grid Cartographer.

The official release of the software runs as a typical stand-alone application and to use it to draw maps involves repeatedly switching back and forth between the DOSBox and Grid Cartographer windows, which can be quite cumbersome.

However, because the DOSBox project is open source, it's possible to modify the code to better suit its use for CRPG mapping. This has led to the development of "DOSBox Gridc", a specially modified version of DOSBox that transmits video information to Grid Cartographer, receives input commands and allows for an integrated picture-in-picture display, as shown here:

dosbox gridc

Note: DOSBox Gridc was formerly known as 'Custom DOSBox'