Good question. According to classification by government (those who has taken a decision about bitcoin), it is a commodity like gold and silver. It is therefore not legal tender.
If you look at the history of money, it was created independently from any government. The community decided what to use as a medium of exchange. It settled on gold, and the characteristics of money became something you can use to measure value, exchange value and store value. History demonstrates the cycle which accorded more than once of the community creating money, the government get involved and destroy it. The latest agreement between the community and government is that the community can create money, but the government with putting its stamp of approval on it to ensure that it has value. This is the reason why the Reserve Banks are private institutes and not a government institution. With the 2008 crisis, the relationship changed when the government starts to print money and to use the Reserve as a government institute.
Back to your question. Bitcoin is not money according to the government, but it is money according to the community as you can measure, exchange and store value with it.