A legacy version of Cuphead has now officially been released on Steam, which is the “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 previous bugs are present in the legacy version. Additionally, using this branch may corrupt or erase player saves.
The new branch offers the strategies from previous Cuphead runs to come back into the spotlight. Some of the patches that came later past the initial release had broken strategies 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.