almost always yes.
you can get away with a straight chainline if you are running a small front ring. the issue comes with the ring hitting the chainstay... you will definitely have to use the inner side of a road double and possibly a BB with a shorter spindle to achieve good chainline, and you will probably have to use a smaller chainring to not hit the stays. problem is, of course, that BMX freewheels come in 15t at the very smallest, and most only go down to 16t... most people will want to run at least a 44t chainring with that.