Complex sentence: It translates G3, G4 and AltiVec instructions, but it does not translate software that requires the G5-specific features of later Apple systems; such applications have to be modified by their developers to work on Intel-based Macintoshes.
Split into simpler sentences: It translates G3, G4 and AltiVec instructions, however it does not translate G5 instructions. Therefore such applications have to be modified by their developers to work on Intel-based Macintoshes.