I have a few questions regarding the rules:

1. Is it allowed to change the color on a per instance basis (for example two times the same sprite but in different colors)?
2. Is it allowed to change the color on a per texture basis (for example I want green gems but the rest should stay black)?
3. Is it allowed to change the color to one with no opacity?
4. Is it allowed to overlay different textures to create a new one?
5. Is it allowed to animate the sprites by either changing the texture of a sprite or by using shaders or cut out animation?
6. Is it allowed to change the assets itself or must this be done by the game itself?

I hope you can help me clarify this.

Thanks in advance.

I too would like to know if changing/adding alpha is considered a color change.

is custom music allowed?

Custom music and royalty free music are allowed

An other question. Under what licence are we allowed to use your assets?  I would like to see something like the CC-BY license.