For me bitcoin is a digital money that has a value that needs mined. As what i understood in Islam if it is halal if it is lawful in traditional Islamic law. Maybe they considered it because they know is is lawful to their tradition.
I think it's money, it's only used digitally. Bitcoin has a value that is converted with USD, so it can be known by the public that today's bitcoin exchange rate is USD. In my opinion it is lawful because it is not gambling, and prices are made because there is supply and demand.