Free to use. Leave the original copyright. You can move it around to suit your needs, but make sure it's still there and visible.

To make it slightly easier for those who colour with the eraser tool on MS Paint, the whites and blacks of the eyes are not pure and the background is grey. So you can eraser-scribble all over the pure white and black without messing up the eyes or background. Also you can fill in colour with the paint bucket tool without trying to go after an irritating missed spot (quadruple-tested it myself X3)

If you want to erase the collar, go right ahead. ^_^