Hard to say. FO3's Brotherhood has a different psychology from past Brotherhoods.
Western Brotherhood had little interaction with the outside world, and subscribed to military discipline (so that maybe means no drugs). Can't comment on their recruitment policies, cause they didn't have any. Cheers!
Midwestern Brotherhood allowed their recruits to take chems to aid them in battle and even traded them within their bases. Don't know if the goodly FO3 Brotherhood does the same. I forgot what they sold in their armory. Might want to check that out. If they sell chems there, then taking drugs might not be a problem for them.
My guess is that as long as you're willing to help the innocent, then the Capital Wasteland Brotherhood will be willing to take you in regardless of past sins and addictions. The Lone Wanderer is a prime example of this.