They already are available. Though, you need to register the key on Desura and connect your game from Desura to a Dischan account where a key will be waiting for you.
If that didn't make sense to you, here's
something that will.
This is the most convoluted way to get a Steam key i've heard so far. Jesus, these Indie Publishers are out of control. They should just give out everything through Desura and through the Indie Bundle you bought it from. AND THEN EMAIL ME ABOUT IT JESUS CHRIST
Mine was Half-Life Anthology, the collector's pack which included Blue Shift and Opposing Force as separate CDs.
Lol, remember that? Using actual CDs to install your PC games, back in the day? How quaint.
Well, the actual first game I registered on Steam was Half Life 2 (I got a key from buying a Radeon 9800 ATI Bundle). But the first game I actually bought with money from Steam was either SIN Episode 1 or Rag Doll Kung Fu. I don't quite remember, to be honest, and I can't check on Steam's "Account Details" because it's not loading.
Edit: IT loaded Partially:
ATI Bundle (Half Life 2 and a couple things. Nice ATI Bundle, my videocard had died already when Half Life 2 finally came out)
Rag Doll Kung Fu (First actual purchase)
Sin Episode 1 (oh jesus)
Half-Life 2: Episode One (and here starts the Steam Salvation of PC Gaming)
The Orange Box (Wait, maybe it was here)
Audiosurf (Oh look, I did buy this really early...)
To think I didn't start buying Steam Games actively until Half Life Episode 1.. good times!