It's one of numerous features the mod adds to TF2's pre-2010 skeleton, alongside reverse-engineered versions of TF2 prerelease weapons like the Nailgun and Dynamite pack, and a chaotic "four-team ...

The mod has been available since 2020 ... “Anticipate new weapons, modes, and characters as Team Fortress 2 Classic grows,” they write at the bottom of its Steam page.

With entirely new weapons and items like jump pads ... and bug fixes." Being a mod, Team Fortress 2 Classic's Steam release will require you to own TF2, but that should be no real obstacle ...