It's not DRM (or even "close to it"), it's a "canary trap", or a "barium meal test". The modern equivalents in images, audio files, ebooks, etc. are usually called watermarks, even though they aren't visible (so sometimes called an "invisible watermark"), and are used extensively (including by ebook publishers that don't use DRM).

It seems like that would be just for the purpose of detection and wouldn't stop people from using either the map or the software.

DRM is bad because it both doesn't stop pirates and hurts normal users. This allows detection of pirates and hurts no one.