A BJ is only cheating if you are in love with the girl giving it. Otherwise, you are in the clear.
I actually have seen 2 individuals who only want bj's & it's because they are already involved, but I'm pretty sure their S.O. would consider it cheating.
Now for me personally because I don't and won't give my S.O a BJ I wouldn't consider it cheating .... I mean somebodies got to do it...