With the PoS (Proof of Stake) setup for the coin Philosopher Stone. Do I have to leave the QT client open all the time in order to receive interest? This coin is based of off PPCoin, so does it do the same thing having to leave your qt client open all the time in order to receive interest?
Short answer: Yes.
Long answer: To make your coins mature, all you have to do is wait but you need your wallet to be open and running the staking process, otherwise nothing's happening.