I'm going to tell you about latest changes for AmigaOS4.1
When we talk about Basilisk its emulator for MacOS7/MacOS8, the different versions the Basilisk II 1.0 was created more or less in 2001 to 2006, after this it was almost no changes to Amiga specific stuff.
jlachmann added video switching in 2001.
cebix did some work on SCSI support.
Basilisk 0.9 comes from Ilkka "itix" Lehtoranta it was ported to MorphOS back in 2005 form a older source code, later it was upgraded with a newer UAE CPU core (from 1.0), AmigaOS4 version was heavily based on 0.9 version for MorphOS, there where few problems whit difference between AmigaOS4 and MorphOS, but the main thing the MorphOS version made easier for me to know where changes things, because CPU emulated, unlike on a Classic Amiga, I also rewrote the MUI based GUI to Reaction, it was simple to do whit few macro changes, the difference between this two GUI systems are not that big they fundamentally work the same way.
The biggest difference is that 1.0 support screen modes, and so you switch resolution whit out quieting the emulator, there are some other thins too, it was much easier to quit 0.9 then 1.0, because 1.0 does some thing strange in the interpreter, recursive callbacks makes it hard to understand what is going on, so this version does not have a quit button.
I have put copied over platform specific code from 0.9 and replaced the incompatible source code whit 1.0 and updated it, some of the changes jlachmann, cebix and gbeauche did might have been lost in the process, as for core of Basilisk 1.0 has been updated to recently a lot of work has done on SDL stuff, we only use the audio part of SDL, because AHI stuff did not work.
So now there is compliantly new video code for AmigaOS4, based on AmigaOS3 code, I have also added the scroll wheel support form 0.9 video drivers, the rest is new code.
Video modes supported are 2 and 256 colors and 32bit, I have dropped the 16bit video mode for now because it has to be converted to 32bit in window mode (slow), maybe add it later.
I have also experimented whit composition because its hardware accelerated, and enables fast scaling, its nice to be able to make where large window smaller, or small window whit low resolution bigger, if your playing a old game.
Disk images has been upgraded, whit support for read only disk images,
you can now also create disk images from the GUI, I have also done few more improvements to the GUI.
Virtual Amiga volume thing, is kind of buggy if you delete .finf and .rsrc directory before start emulator it work perfect or else you can get DSI error you can ignore, the best thing to point it to RAM disk, I think.