A legacy version of Cuphead has now officially been released on Steam, which is the same “exact launch build as Cuphead, with no applied patches and no future support”, StudioMDHR announced on patch notes from December 20th, 2017.
The Legacy branch contains exploits and bugs of the launch version, however the legacy branch will not be supported nor modified in the future. This means that the bugs previously present are present in the legacy version, and that it may corrupt or erase player saves.
The new branch offers the strategies from previous Cuphead runs to come back to light on said branch. Some of the patches that came later past the initial release broke skips and glitches discovered that had accelerated the speed of completing the game.
For the speedrunning leaderboard, however, this doesn’t change much. Current runs of Cuphead categories excluding Glitchless are ran on a “Legacy” board, where the version is downpatched.
This legacy branch is available only to those who have the Steam version of the game.