I don't think it needs to have permission to be trained on
If you go to a museum right now and go look at all of the old artists paintings, are you getting permissiont to add that to your brains memory and call upon it when you go to draw your own?
First, you surely know that even in the case that an artist recalls perfectly another work, copying the data is still... well plagiarism.
Secondly, the brain doesn't work like the AI program does. When you add to works of another artists on your image memory bank, you don't copy and paste those different works on your own work. Yet, this is exactly what AI is doing. It only copies and paste based on data bank and a matrice of pixel, it doesn't imagine or use anykind of knowledge to create. Which means that without the bank of images the AI is trained on, there is no final product at all when there is one for a human.
Human uses their memories and other's work only as inspirations. They don't need it to create great art. In fact, its perfectly possible to become a skilled artist without even accessing any kind of data from other artists.
So, when the work of artists is being used to train AI and make profit out of it, its called stealing, and for a good reason.
Now apply this to learning from other artists as we do. If we don't have to get permission, then AI doesn't need permission.
Doing art is not simply drawing, playing the flute and shaping a bunch of wet stone.
Art is about understanding our reality, how it works, how it is shaped, how it is lighten, how its sounds, why it is the way it is...
.. Taking all this knowledge through our own history and values and personnal context...
.. and shaping it back into a new form to touch the emotions of others.
There is no such process in AI usage. The AI uses works from artists to copy and paste what the training made it learn to be reality was without understanding of it and therefore no chance to expand beyond limits. Ai is by essence limited by the median point of all the ressources in its data bank. It can't go farther.
Now, as long as people will profit from AI trained on the work of other artists, those artists will militate to stop the AI based on copyrighted material.
So.. as an artist, you would be wise to understand that if a tech bro with an AI tool can use the work of copyrighted material of artists, they can also use the AI products of other tech bros who are using this same tool to produce more AI "work" and therefore profit out of it and replace the first tech bros with themselves until another tech bro comes along.. and so on... and so on.. and so on....
.. until AI based production and the entire artistic industry implodes on itself thus putting hundreds of thousand of people out of work.
But yey !!... Progress !