You have to wonder how any company could get away with so brazenly using the word SUPERMAN in big block letters in their logo... in 1941 -- but Russ Winterbotham went to great pains to provide a 2-page explanation, right up front, of exactly what a (generic, no capitalization) "superman" is. It also probably helps that Maximo has no costume. He is, in fact, a mutant -- a younger, handsomer version of Professor X (by way of a little inspiration from Doc Savage). Winterbotham also wrote his share of pulp sf stories, so he could claim some authenticity of authorship.
Link to the book:
Maximo The Amazing Superman And The Supermachine