You know how many times I’ve had straight friends I wish would ask me to blow them or experiment? Guarantee this guy is sitting by the phone every night waiting for you to ask this question.
yeah - I don't know if I'd guarantee that at all and makes it sound like gay men would just swoop at the opportunity of having sex with a straight mate just cos ..
Maybe the gay friend is just happy with having a mate and doesn't feel attracted to him at all .. or maybe he has been secretly lusting after him all this time.. I'm guessing this gay friend has some sort of say in all this that involves something around how he feels about this guy rather than just some general " if you are straight and have a gay friend 100% he wants to fuck you" .. I'm bi - have loads of straight mates and women friends - the vast majority of which I have absolutely no desire to even see naked let alone screw.
My advice would be to tread carefully. Making a move could be absolutely fine resulting in a mad nights romp or a polite "nope".. or it could change the dynamic forever.
If there is reason to believe he is attracted to you - then I'd explore that a bit and bring it up at some point letting him know you're game. If there has never been any suggestion that this guy finds you attractive - like at all .. I wouldn't be acting on the assumption that making a move will yield results.
I'd start with a conversation around what sort of guys he finds attractive and see where that goes ..if there is any interest at all, you're leaving the door open for him to say "well, guys that look a bit like you.." or something to that effect.