A page listing ports to other platforms is at (hey there's an Arc port and an Amiga port!!! We've got to get an Atari port started now!!!)
http://www.mozilla.org/ports/
And the page where source can be found is at :
http://lxr.mozilla.org/seamonkey/
Perhaps just by accident i have kicked off what could be called an 'exciting development'. Too bad the Milan 2 will never be around now to see it ... :( That would have been sweeeeet...