ArchiCAD 13 -
ArchiCAD 13 and over are only available for Intel-based Macs.
ArchiCAD 10 to 12
ArchiCAD 10 to 12 had both PPC and Intel Mac compatible versions.
ArchiCAD 7.0 to 9
The Rosetta environment is discontinued in 10.7.
ArchiCAD 7.0 to 9 had only PPC versions and therefore can only run using the Rosetta environment on Intel Macs.
Mac OSX 10.7
The Rosetta environment is discontinued in Mac OSX 10.7. Read further details: MacOSXLion
Mac OSX 10.6
Rosetta is not included in the default Mac OSX 10.6 installation, but there is an option for installing it: http://support.apple.com/kb/PH6531
Security update 2012-001 conflicts with old ArchiCADs: SnowLeopard
Mac OSX 10.5
Rosetta was included in Mac OSX 10.5.