Brian
I'm sure that the BSAOC [in the UK] do their best to keep everything legal, and just by acting as the "Authority", they are helping us keep our prized chargers on the road. Without their help a lot of bikes which turned up in the last 20 years or so wouldn't have been registered, or would have ended up on crappy Q plates. Our government agency in the Uk wouldn't be bothered to sort out records to prove the age of a vehicle, and we the BSA owners would be worse off.
Records are available and they will issue them to members for a small fee, I think its a good thing to be a member, I support them through the membership and they help me via their services.
Its nothing to do with the originality of any particular bike, its to do with Legalities.
There are indeed a large amount of fake Goldstars, but imagine if their was no control at all. BTW, the Goldstar owners club is separate to the BSAOC.