For those who are wondering why this shows up in Software Update, even though you don't have iLife '09 installed...

Software Update detects that you have iTunes (technically part of the iLife Suite) in your Apps folder, so it assumes that you have the rest of the iLife apps. If anyone recalls, the same thing happened when iLife '06 users were prompted to apply the iLife Support Update v8.3 (for iLife '08).

So, if you don't have iLife '09, you can ignore this update. If it works the same way as the previous v8.3 update, then you'll just get an error message telling you that it can't update the iLife '09 shared components because they aren't present.