It might work with AROS though, right?
No, but an open source Settlers clone which is ported to the Amiga could also be ported to AROS.
Which brings me to a question, if hardware hitting apps can run on UAE, why dosnt AmigaOS just use those parts of AROS that allow those sort of programs to run? Something to dow ith the licence?
Hardware hitting apps can not run on AROS, unloss AROS is running on original hardware. AROS is an Amiga OS clone, not a hardware emulation like UAE. This means that no Amiga binaries will ever run on AROS on x86 or PPC hardware. In theory Amiga binaries could run if AROS was running on 68k based hardware (It would have to be a real Amiga it the software accesses the custom chips though).
In short, the only way of running Classic Amiga apps/games which bang the hardware is through UAE or on a real Amiga. This is true for Amiga OS4, Morph OS, AROS and Amithlon.
AROS doesn't even have 68k emulation (which AmigaOS4.0, MorphOS, Amithlon and UAE all have) so it can only run Amiga 68k applications if it is running on a real 68k processor. In the future it probably will get a 68k emulator which will bring its Amiga compatibility in line with OS4, MOS and Amithlon.
Amiga games were rarely designed with multitasking environments in mind anyway, I think you will always be better off running them under UAE to prevent them trashing your system.