Yair, limited account users can't install software... Nor do I recall an option upon install to allow other users to access it, as some software does. Also, the Parental Controls includes a list of approved applications--Leaf doesn't appear on the list automatically. When I add it manually, I get an error that the configuration I am attempting (giving the user access to Leaf) is not supported.
BTW, Leaf is the ONLY software I can think of that acts like this--Adobe CS3, Office, etc. etc. can be run by limited accounts. And Parental Controls offers supporting application files the ability to run, should that be the next thing to consider in our troubleshooting.
Sort of a Catch-22. Please offer more details if you feel this should work (such as, do you mean I should move Leaf into the students' Applications folder? I haven't tried that yet). Otherwise I have to let students be admins on a couple of G5 iMacs and hope for the best!