I am afraid iMacs are not very likely to be officially supported. The integrated LCD display does degrade over time and loses brightness, contrast and overal quality of color reproduction.
This also applies to laptops with integrated displays to some degree, but the portability and ability to use MorphOS "on the go" makes up for it.
With regard to desktop machines, a combination of either a Mac Mini, PowerMac or a Powerbook in "desktop mode" (closed lid) and an external modern display is a superior option to old iMacs.
