I misspoke. (Err mistyped?) I suspect there will often be a stronger case to be made for the model itself falling under copyright than what it outputs. It's up to the courts and the legislature in the end though, so who knows.

Anyway, by providing public access to this thing I infer GitHub to be taking the position that copyright doesn't apply to the output. (And I suspect they are wrong, in particular because of the verbatim code samples people have managed to coax out of it.)