I think he is and I have proof:
In the English dubbed version, the one where they first go to Cerulean City, James says something along the lines of: "It's times like these that make me want to go straight!"
lol i think he just do those things for humour. After all, he's a rich, weak kid. And, he is engage to a girl who looks like Jessie. Also, i think he has some affection for Jessie.
Well in the cartoon its geared towards kids so they make him a sissy as they can cause its funny. In the anime/manga he is not gay and like the other guy said on here gets married to jessie.
American adaptations of anime/manga are so disgraceful I almost always end up going online and downloading the japanese version with subtitles cause I can't take it.