Mac Informer client works with Mac OS X 10.5 up to 10.9. You can download it through its official page at Mac Informer. I don't know it if works for versions prior to the 10.5 release, but if you have the possibility, you can try it for yourself. During its release times, I have installed it on all the versions between 10.5 and 10.9 and it worked normally without bugs or errors.
