to answer ur question on Smush IT, tell me first.. are all the functions/features on the client side, IE a selfhosted API endpoint, or is it a remote service on WPMUdev server - > the latter / remote then theres nothing u can do buy $$ it. If not, then yeah u cna tell api key to take a hike.
also is API key for WPMU, or is it for a 3rd party webservice.
i believe this ewww image optimizer is better choice than smushit but thanks for the share