Plato is a commercial product and requires a paid license for possession or use. Using Plato is subject to the terms and conditions of the Plato EULA at https://plato.instantasp.co.uk/legal/license.
To acquire a license, you can purchase one at https://plato.instantasp.co.uk/pricing. A free open source license is also available for open source projects who have less than $250,000 USD in annual gross revenue - https://plato.instantasp.co.uk/open-source