This is something I've dealt with with Sims 3. (I dislike building in 4, so I haven't done more than remodel a few existing homes). I like the challenge of making things as close to the real thing as possible. I had some builds that someone else re-uploaded as their own. They didn't bother to even change what I'd typed in the description box. Maxis said that you could request items be removed because they were plagerized, so I did several times. Nothing happened, so I gave up and just removed the items from my studio. After sulking about it for awhile I decided I still wanted to share them and put the items back in my gallery.
I think that once something is uploaded Maxis considers it free game unless there is a copyright involved.
It is rude to re-upload something and claim credit. It's basically stealing someone else's intellectual property. But, the exchange and gallery are places to post where we have no legal claims. It's all free with no copyrights. So we just have to decide whether we want to share- and risk it being "stolen" or not. Unless Maxis implements a way of protecting the original builder, there is nothing we can do.
