"Won't touch it unless it's official" Edition
For all your questions on Dark Heresy (1st and 2nd Editions), Rogue Trader, Deathwatch, Black Crusade, and Only War.
Not the wargame, not Chapter Master, not Space Hulk. Inquisitor is okay, but not many people know about it.
Not sure between starting Dark Heresy 1e and 2e? Pick 2e.
>Why did FFG lose the 40k RPG License?
Because they were bought by Asmodee and that caused some sort of licensing conflict.
>Will GW make their own 40k RPGs now?
Probably not. But if they do it will likely be worse than you could possibly imagine.
Book Repositories (If you're planning to download any Rogue Trader materials, read the .txt file in the RT directory)
There is a new Homebrew Megafolder option in above MEGA directory containing several things.
40K RPG tools, a site that contains stats or references for almost all weapons, armor and NPCs/adversaries. Not updated past DH2 core.
40k RPG Combined Armory (v6.48.161023), containing every piece of gear in all five lines. Now includes all DH2e books.
The Good, the Bad, and the Alpha Legion (v1.0.0) (Total Conversion Deathwatch into the Horus Heresy)
Mars Needs Women! (v1.2.15) (Mechanicus Skitarii and Taghmata for Only War)
Fear and Loathing in the Eastern Fringe (V1.6.4) (Playable Xenos for Rogue Trader)
The Fringe is Yours! (v1.8.13) (More Xenos, Knights, and Horus Heresy gear for Rogue Trader)
Besides the Horus Heresy and the modern Dark Millennium, do you ever consider running games in other periods, like the War of the Beast or the Macharian Crusades?