I love Open Game Art. It's a fantastic resource to have when creating games. It has helped me out with a few prototypes, which would have taken a bit longer otherwise. It is wonderful that we have a website like it, giving people a free source of assets to pull from when they need, no strings attached. After I used assets from Open Game Art, I uploaded something of mine (an early version of a 2d character template I use) to pay it forward.
Originality is getting harder to find, and there is nothing wrong with having things that you can reference, use, and work from without fear of the possible repercussions. Things like Open Game Art are a fantastic source that need to be bigger than they are now.