It's been a long time coming, but you can finally Steam-ify your own maps in Rise of the Triad 2013.
Rise of the Triad received an update to version 1.5 today, bringing Steam Workshop integration and a free weekend with it.
ROTT 2013's level editor was introduced in the v1.2 update, but there was no established central hub for sharing maps (aside from those eventually, officially supported by Interceptor Entertainment). Steam Workshop support solves the problem, so Rise of the Triad players can now create, upload, and share maps within the Steam client.
Among the most notable community-made maps so far? Doom's E1M1 (Hangar), and Hollywood Holocaust from Duke Nukem 3D. Given the nostalgia-fest that is Rise of the Triad, I'd expect to see virtually every single-player map from every 90's shooter ever made, ever, to make an appearance on Steam.
To help get the v1.5 word out, Interceptor has a free Rise of the Triad weekend going on right now, so H.U.N.T. newbies can give the game a go, gratis, up through 1pm on Sunday, October 5th. Additionally, the original Rise of the Triad (Dark War) can be had for $2.49 through the on-sale Apogee Throwback Pack.