I'm no legal expert, so when I tried to find whether or not the Icons of 13th Age mechanics are OGL or not, I failed. So, erroring on the side of caution, I won't put the rules there.
For my game, I'm not even going to use the die roll mechanic every game. I feel it will dictate too much on how the session goes. Instead, I may ask for a roll if the characters are dealing with somehting in the Icon's purview. I'll go back and re-edit that first paragraph (along with the edits you mentioned) to solidify that idea.