given what they did with Damnatus, I suspect they would be more likely to reach for their lawyers.
Not necessarily.
There's another WH40K movie, also on YouTube, called
Guardsman.
The
behind the scenes video is pretty good too.
Apparently, they were able to get one of the GW/Black Library people to be a voice actor near the very start of the movie, but it is still an independent effort, and as far as I can tell, it's not officially endorsed by Games Workshop.
That said, the people at GW liked it enough to invite the creators to work with them on the upcoming, officially licenced animated series, "Angels of Death", which was announced in December with
a teaser on the Warhammer TV channel.