The purpose of installing an application on a terminal server is to make that application available to multiple clients, i.e. multiple persons. This, however, is in contradiction to the yEd software license, which doesn't grant the right to use yEd as a network application by multiple persons.
If you really, really want to install yEd on a terminal server and make it available to multiple clients, please don't hesitate to get in touch with our sales team to discuss the available options.