Bitcoin is definitely taxable. If you sell all of your bitcoin for USD you pay a tax on the profits. Make sure to check with your local government tax office before failing to pay taxes.
no it is not tax, it is just the fee you pay on transaction, the tax you have to pay to the government and government only impose tax on such things which are legal and do not impose tax on such item which are not legal, as bitcoin is still not consider as legal therefore there is no tax on bitcoin.