I'm more familiar with NT's internals than Amiga's, but I'm sure Amiga is what influenced the design.
Though Amiga was more of a true microkernel but without memory protection; NT and DragonFly have memory protection but the kernel is a single executable composed of multiple message-passing modules.
Re:DragonFly BSD 4.6 Released
by anexprogrammer on Wednesday August 03, 2016 @06:16PM
(#12221985)
I'm fairly sure, around the time of the original fork, Matt announced the intention for DragonFly to take inspiration from the Amiga for some aspects of the new OS and kernel. Messaging was one of them. I forget the others.
Given Mr Dillon's background I'd have called it Amiga-ish, but perhaps that's just nme.