Gridcoin is described as 'cryptocurrency that rewards scientific computations on BOINC' and is a Cryptocurrency Coin in the Bitcoin & Cryptocurrency category. There are more than 25 alternatives to Gridcoin for a variety of platforms, including Mac, Windows, Linux, Online / Web-based and Android. The best alternative is Bitcoin, which is both free and Open Source. Other great apps like Gridcoin are Monero (Free, Open Source), Ethereum (Free, Open Source), Litecoin (Free, Open Source) and Dogecoin (Free, Open Source).
Bitcoin is a peer-to-peer digital currency. Peer-to-peer (P2P) means that there is no central authority to issue new money or keep track of transactions. Instead, these tasks are managed collectively by the nodes of the network.
Monero is a digital currency that is secure, private, and untraceable. It is open-source and freely available to all. With Monero, you are your own bank. Only you control and are responsible for your funds, and your accounts and transactions are kept private from prying eyes.