For many years, (painters) artists have set up in museums to copy the works of the masters--with the understanding that the work is attributed to the master and can only be sold as a copy. Most artists wouldn't even think of selling them, but would gift them to family or friends. The attribute is plainly shown on the FRONT of the copy/ It is an integral part of the painting. This was a good way to learn different techniques, and the original painter wasn't around to ask permission. It was accepted with restrictions.
Back in the day when I headed up juried art shows, we would usually have at least three paintings entered that were direct copies of photos from National Geographic. Those were returned to the submitting artist with a short bit of literature on copyright infringement. Some learned from this, others--never.
Copy if you want to learn techniques, but for heaven's sake, learn and burn!