Why? With the build prerequisites (VS, DX SDK, Mozilla build tools) it seems like an awful candidate for porting. So much, in fact, that the Linux port is maintained as a separate project.
Looking at the feature list, the only feature that really stands out is that it's "optimized for modern processors", which of course is a disadvantage in running it on any Amiga or Amiga-like.
Admittedly, I've never run Pale Moon, so I have no idea what its advantages really are, but given their focus on the Windows platform and modern processors it does seem like the worst of the modern open source browsers to port to the Amiga.