I don't think it's a legal issue. The "Legal" label is actually a link (perhaps a UIButton?) pointing to a legal document.
The sole purpose of MKMapSnapshotter is to create images for a specified map region/rect. The output is an image where the "legal" link would not serve any useful or legal purpose.
Please also note that MKMapSnapshotter is an official Apple API, in other words it is Apple, not you, who actually removed the "Legal" label/link.