It’s part of a movement to ensure that artists are fairly compensated.
The issue is becoming more urgent as generative AI programs grow in popularity.
“Right now, creating art in the artist’s or artists' styles is easy to do.

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AI image generators aren’t really copying the art they’re trained on.
Cameras and tape recorders allowed paintings and music to be recorded, copied, and sold.
Digital copying allowed copying to be industrialized.

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AI is no different.
Maymar pointed out that sites likeHave I Been Trainedshow if your artwork was used to train the model.