I think part of the goal of bitcoin was to be deliberately confusing in that way.
If the govenrment wants to impose strong Money-Service-Business regulation on Bitcoin use, claim it is a commodity.
If the government wants to claim VAT, claim it is a currency.
Of course, now in the US different branches of the government have started choosing those same contradictory interpretations when it suites their purposes. (IRS: commodity; Fincen: Currency)