I think that System Requirements entry for iPhoto 9.4.3 is incomplete. I believe it should read:
OS X Lion 10.7.5
OS X Mountain Lion 10.8.3
or latersince the System Requirements entry for
iPhoto 9.4.2 reads*:
OS X Lion 10.7.5
OS X Mountain Lion 10.8.2 or later
I had a look at my Mavericks volume—10.9.5, and I was apparently running iPhoto 9.4.2, so although I didn't really use iPhoto much, I'm pretty sure that version is compatible.
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*Yes, I know this link is for a US locale!