> Somebody tried to boot morphos on an imac G5 ?

Yes:
https://morph.zone/modules/newbb_plus/viewtopic.php?forum=11&topic_id=9034&start=57

...but as geit already said:
https://morph.zone/modules/newbb_plus/viewtopic.php?forum=11&topic_id=9034&start=50

> i remember to have seen an imac g5 picture running morphos somewhere

More pictures there:
https://morph.zone/modules/newbb_plus/viewtopic.php?forum=11&topic_id=9034&start=63

Latest statement from the responsible developer:
https://morph.zone/modules/newbb_plus/viewtopic.php?forum=11&topic_id=9034&start=68