Cryptocurrency has always been taxable, the basic question is what constitutes a gain, and when the tax is due. The trading of cryptocurrencies is also clearly different from the mining of them. My own understanding is that the €12,000 value that I have apparently gained in the last month on Steemit only becomes taxable when it is cashed out into fiat. Likewise with my Gridcoin holdings, as it is my Euro gains that matter. Different tax rates may also apply. In the case of Steem I am earning income from writing, but in the case of Gridcoin I could be regarded as mining it through BOINC activity. In all events expect to see compulsory registration of cryptocurrencies soon.