Was it not the case that the BDS was formed by the original DDM members who brought ideas, knowledge (and targets) back from Germany? Long before my time, but your MOD buck target would appear to substantiate this?
I'm not sure whether you are suggesting that the BDS should have recognised DDM or the DJV or possibly both?
It's just a target at the end of the day, and probably not subject to copyright laws any way.
However, the history is very interesting, and that target will be worth a few quid if you still have it? The history of deer management in UK seems relatively 'young', which is why someone like yourself should document it H!

Regards,
MS