The term has nothing to do with homosexuality in and of itself, although it might be on the borderline sometimes. For example if a straight guy really enjoys spending time with his male best friend and has lots of sentimental feelings for him that are perhaps stereotypically 'Un-American', he is said to have a 'boycrush.'
Because of our society, it's probably quite common for somebody to hide their innocent boycrushes.
"He talks about his favorite sports hero so much, you would think he had a boycrush."
"The male cast members of 'Friends' sure had lots of boycrushes on each other."