That script just prevents the map from loading in Zandronum, and Zandronum has the best anti-lag for multiplayer. Jumping can be disabled with dmflags. Is it possible to remove that script from the map?
The map doesn't run in Zandronum, shows "Unknown player class 'NoJumpPlayerPawn'" error. Probably, some script is not compatible with Zandronum. However, it runs in more vanilla ports that ignore scripts entirely.