Wolf4SDL is an open-source port of id Software's Wolfenstein 3D to the cross-platform multimedia library SDL. The port has especially benefited those who use machines that no longer natively support DOS.
Wolf4SDL was developed by Ripper, who based it upon Wolf4GW. The port was first released in late December 2007, slowly starting a new wave of mods and TC's that could use the new, expansive port to create mods that would have either been hard to do or impossible to do in the DOS format.
Wolf4SDL remained popular ever since, though today numerous other ports exist, including ECWolf.