CoinUrl has no ads displayed but you have to click a button to go to the intended link, so i would assume that this is "an additional step". Did i get it right?
The unofficial (official) rule states:
"5. No link shortners that requires users to view an ad."
So that
could be alright (as long as you absolutely don't get anything that can be even mistaken as an ad).
However, since you're going to make revenue via coinurl (not very familiar with them, but you earn for clicks there, correct?), I can totally see the rule also being enforced on those.
To be honest, I find those kind of shorteners annoying, and I wouldn't advice you to use them/wouldn't use them myself.
Actually, ignore that, I've checked them out.
They display a
text ad, hence are clearly against the rule.