To port it to AmigaOS would require the use of either Holger Kruse's X11 port, or Dale Luck/GFXbase's port, neither of which are available/being sold at the moment.
Holger Kruse's X11 port, called AmiWin, is _available_. You can use it ... you just can't register it because Holger has been unresponsive to the Amiga community since he went to work at REBOL. I don't know what limitations it has without registration, but it seems to work perfectly fine for me when connecting to UNIX servers at work from my home.
Go to
http://www.nordicglobal.com and click on the "AmiWin" link. You can download it from the "Software Download" link on the left side of the page.
@frankb,
As far as Mozilla being available _right now_ for Amiga, that user on IRC was pulling your chain.
