If it's dating a few different girls prior to actual bgr
commitment, then I don't see what's the problem. So long as you're
not in a relationship, you have the right to date anyone you
want.
Of course, if it's your intention to woo both girls at the same
time, then that's a no-no. Goes to show that you're not being
sincere with either of them.
If it's during an actual bgr, then it's blatant two-timing already.
Definite no-go.