I voted for commodity; I did this based on the active definitions of a currency vs the definition of a commodity.

Ultimate, since BTC is technically finite, I think it has to be looked at as a commodity since its value is very much defined by market operations, and if not now, then eventually, by supply and demand.

I think it's intent is certainly as a currency, but it's current characteristics, to me, really do not align with that of a currency (not backed by a Government FIAT, not a slowly decreasing inherit value if held.

Ultimately, in it's current state, BTC almost acts a currency that is backed by a commodity, although strangely it's almost itself as the commodity too.

Bottom line though, I think that because BTC, by definition, has a finite value, it ought to always be considered a commodity (keeping in mind that commodities can easily be used as currencies).