I find it funny how DragonFly keeps coming up as a buzz word among amiga users, but how many of those mentioning it has actually used it?!
I do have it installed in a VM but did not actually use it much. I'm more a Linux guy than a *BSD guy.
The reason DragonFlyBSD is mentioned is of course because of Matt Dillon who has a history in the Amiga world. (People who know what a Fish disk is should also know Matt and DICE).
He did base some of the internals of DF on Amiga architecture. AFAICS they are not exported to user land but I think that is the first thing to do for a retought incompatible Amiga-like OS.
Personally I think anyone who want to come up with a totally new OS architecture is DOA (dead-on-arrival). The OS market is mature enough that I think it is impossible to get track on something totally different (see it like the flying cars etc.). GNU bootstrapped on commercial UNIX, Linux bootstrapped on GNU, Android bootstrapped on Linux, all *BSD bootstrapped on original Berkely UNIX, MINIX is now using NetBSD, Win NT has links with VMS although there are debates on how strongly they are, ...
Although my AROS dev work (any Amiga dev work actually) is really low to non-existing at the moment one of the goals for me was to see how far one could go with the Amiga architecture and API without breaking backwards compatibility.