You may use my art however you want, non-commercially. Commercially defined by me as money being given to you for art that I made.

You may use my art commercially if you discuss with me beforehand your plans. In general, you may use my art commercial if the main thing you're selling isn't my art- for example, you MAY use my art on trading cards that you sell with other information on them. You MAY NOT put my art on a t-shirt on zazzle and sell it, even with credit from me. Furthermore, using my art commercially may involve higher prices or an agreement to pay me based on what you sell.

You must always credit me with a link back to my DeviantArt somewhere where it can be easily found by those interested. You may never claim my art is yours.
You may not remove my signature or watermark, by image manipulation or cropping. The only instance where you may have my signature non-visible is in a thumbnail that links to the real, signed version. If you really need a non-signed version, I will provide it on my terms, which will be discussed before I ever make the artwork.

If you think you might have a case that would be an exception to my rules, don't be afraid to ask. I am willing to negotiate on a case-by-case basis.