Yup; males have that black marking on their hands.
The Oscars do not bother them. We have had this tank for a few years now like this with not so much as a bite mark on anyone. We feed the Oscars on the cichlid pellets, and the frogs congregate under and beside them and eat the food that they disperse when they chew. I think what it is, is the 2 Oscars we have are not that aggressive; I have had some in the past that would have gladly devoured the fish by now. But it really is weird with Oscars; some are as docile as anything.
I have 5 frogs in all; I will eventually get pics of everyone; 1.2 albino and 1.1 normal.