I'm very curious about what sort of work was involved in such a project. Presumably there was some sort of relatively low level compatibility layer involved, since Marklar was kept updated to run 10.2, 10.3 and 10.4, apparently with a small team (Quora post said the guy needed a project he could do alone).
There were at least two other successful ports of MacOS to x86 back in the pre-Steve days, both described in Jim Carlton's book "Apple." Presumably those ports were trickier since they were porting code originally developed specifically for 680x0 chips rather than originally developed on a portable Unix-like operating system. Still, they were able to get things up and running remarkably quickly. Performance and bug fixing and third party compatibility were another matter.
Carbon et al was an issue. Rosetta wasn't there until the very end. You can get an idea of the lower level work by diffing the divergent Darwin sources from the time (two source branches were used, and Apple released distinct x86/ppc source drops)
There were at least two other successful ports of MacOS to x86 back in the pre-Steve days, both described in Jim Carlton's book "Apple." Presumably those ports were trickier since they were porting code originally developed specifically for 680x0 chips rather than originally developed on a portable Unix-like operating system. Still, they were able to get things up and running remarkably quickly. Performance and bug fixing and third party compatibility were another matter.