In general, I don't have a problem with people using the tools and icons that I put up here, but asking permission and giving credit is something that I generally expect, unless I explicitly say that it's a free-use image. Occasionally, I include icons and tools that are themselves adaptations of other peoples' work. In those cases, I try to give credit, and if I can directly attribute the work to a specific person or site, then I generally refer people to the original work.
In the case of this dragon icon, I'm happy to let other people use it, and I ask such people to credit me and post a link to my dA page.
(I already settled this question by pm, just posting this for people who might have similar questions)