These integrations are all made by our affiliate partners. For customers that use both programs, these e integrations are made to act as connections between the two. There are no extra charges from Clio for using the integrations, however, there may be restrictions from the other company as to which plans have integrations available to them.
No, 3rd party integrations are not free. You will need an account (most likely paid) with the integration company, even as a Clio customer. Their prices should be available on their websites.