Is activated carbon classified as organic or inorganic?
While nomenclature is of particular interest to organic chemists to specify an exact compound, the classification of X into broad category Y or Z isn't a precise science, and not really of practical use.  The article cites a textbook by Seager to this effect, stating 


  The distinction between "organic" and "inorganic" carbon compounds, while "useful in organizing the vast subject of chemistry... is somewhat arbitrary"


Even if you find a source that says "charcoal is (in)organic", you may just as well find one stating the opposite.  Just like the coal from which it may have been produced, it was once biomass and decidedly organic, but so was graphite and diamond, or CO2 and CO32&minus;. I think it's overly pedantic and unproductive to try to come up with definitive judgements for these decidedly edge case scenarios.

After all, it's just a chemical on the shelf, what one does with it is far more relevant.  I don't use it on a daily basis, but it seems more like a tool than a reagent.  The fact it contains carbon seems beside the point; it's value isn't in the chemical composition but rather its extraordinary adsorptive properties.