I wanted to raise awareness of content theft by artists. In my experience talking to many many artists and gallery owners, the majority of problems with copyright violations are simply due to ignorance of copyright law. Yes, it is usually illegal (not to mention unethical) to just take some random picture you got from "somewhere" on the intewebz, upload it to SL and sell it for profit. In some cases that I've looked into, it's deliberate, some "artists" is uploading images blatantly stolen from somewhere, and deceptively passed off as their own for profit. But this is thankfully rare. In almost all cases I've seen, it happens simply due to ignorance. People are under the mistaken impression that just because they find an image on google search or that they got from Uncle Bob in email that there is no copyright associated with that image. Or because they got an image for free, it is ok for them to resell it for a profit.
Gallery owners need to do their part to avoid content theft in SL, and I consider using content or graphics from outside of SL that they do NOT have permission to sell as content theft, plain and simple. If it's wrong to snarf a texture of someone else's painting in SL and sell it, then it's wrong to upload something stolen from outside of SL and sell it as well.
What to do? Be SURE to ask any artists whose art you are displaying this simple question: "Are YOU the content creator of these textures and/or prims? If no, do you have legal permission either via license or from the content creator to sell them?" Just because they created the prim that their texture is slapped on doesn't mean they didn't steal the texture. So check with your artists, don't assume. Don't be an unwitting partner to the sale of stolen goods. You have a responsibility to ensure that your gallery does NOT participate in content theft in any way, shape or form. At the same time, don't assume that an artist that is a bit ignorant of the law is an evil scumbag. Some well meaning people just don't think about these things. Make them aware that it's wrong, it's theft, and we don't do that in SL, where many people make a living off the things they create.
At that point you will need to use your best judgement on whether the theft was indeed deliberate or not. If I were you, I'd err on the safe side and seriously consider asking that artist to pack up and leave unless you truly are convinced it was simple ignorance. If you have any questions or want a 2nd opinion, or would like an independant 3rd party to confront and discuss the issue with the artist, please let me know, I'd be glad to help.