Commander Genius - an open source port for Commander Keen 1 through 6.

It includes features like:

Mod Support with some extras using Lua
OpenGL Acceleration
SDL 2.0 Support
New graphical effects
Multiplayer Support (Up to four players)
High Quality Packs which make the game look better, provide better sounds and even music you might never have known existed in the original games
In-game Menu for Vorticons Keen as well as a new HUD
Named save slots
Unrestricted Joystick Support

and much more