Either Cubicle 7 or Modiphius.
A licensee doesn't have the authority to designate it's licensor's IP as open content. GW itself would need to sign off on that, and that ain't gonna happen!
I could see their being an attempt to make a 5E version, but it would be tricky to reconcile D&Ds Class system with WFRPs career-path system without losing some of the flavour. The actual game in play would be fine though.
So I definitely want a new WFRP game but please by Sigmar's Twin tailed comet, don't make it a 5e game. It will ruin the WFRP old world.
Why do some people think WFRP4 will be set in Old World setting and reusing previously published content? GW want the old fantasy setting forgotten, dead and in Morr's realm so supporting any spin-offs that keep it alive (or undead) go against pleasing the shareholders.
Their approach to licensing doesn't seem to support that view at present though. See "Warhammer: Total War": released after Age of Sigmar, rooted in the Old World setting, with plenty of expansion packs scheduled.
World War Cthulhu, Cthulhu Britannica, and Lone Wolf Adventure Game were all Kickstarted C7 lines, and all three are licensed. But I expect that Chaosium and Joe Dever (RIP) had less-restrictive licensing terms than GW does.Also, I do not remember C7 doing any of their game lines on Kickstarter, or at least none of the higher profile, licensed stuff.
rehashes of what has been done 3 times already?