Yes, GRC is (almost) proof of stake coin. By holding balance in your wallet, which must be unlocked and online, you are eligible to "stake"/create a block. This block will give you Interest reward on your coins and Research reward if you do BOINC. You can earn or mine gridcoin this way. However be warned that it requires considerable balance (thousand) and great load of patience.
If you do not want to invest, but still earn, consider joining the pool.