- dj64 produces 64-bit code, djgpp produces 32-bit
- dj64 uses ELF file format, djgpp uses COFF
- dj64 allows to use host's gdb, djgpp uses some old DOS port of gdb
- preliminary unicode support
- mostly complete BSD sockets support
- out-of-the-box ncurses support
The resulting programs run on the emulated DOS environment, with eg dosemu2 emulator. In theory the 64-bit DOS extender can be written to run such programs under the bare-metal DOS, but the future of DOS is probably in the emulated environments anyway.