I'm pretty sure that if it were toxic to ingest, they wouldn't do so. All the money in the world isn't worth putting your health in danger just to please an audience.
As for whether it's pee, probably. Pee can be clear sometimes, particularly if you eat a healthy diet and drink tons of water. Back when I drank absolutely nothing but water every day for months, my pee was just as clear as the water in the toilet. The more hydrated and healthy you are, the less yellow your pee will be.
Even if it isn't pee, does it really matter? Porn is often fake or staged, mixed in with lots of awesome real sex and masturbation, to help consumers get their rocks off. We enjoy movies with all their special effects, costumes, makeup, and scripting, and we know they aren't real, yet we love them all the same. Why should porn be thought of any differently? If it looks good, feels good, and makes you hot and horny, then it's good.
