NetBSD won't run on WinUAE as it needs a CPU with an MMU (Memory Management Unit), as do all Unixes.
There is a patch on the main UAE site for MMU support against UAE 0.8.20. If you're brave and are prepared to compile WinUAE you could try patching it in. The patch claims to have allowed the author to run m68k Linux under UAE.
It would be nice to see this patched in some time (if it's good enough quality) as then getting AMIX (AmigaUNIX) running under UAE would be possible (maybe).
[Signature removed by Cody - please see the English Amiga Board RULES]