What jurisdiction are we talking about?
In the US, barter is taxable. You haven't specified what the payment in #1 is for, but if it would be taxable as cash it will also be taxable as bitcoins.
Suppose you mow someone's lawn and they pay you with cash. The cash is taxable income. Now suppose instead they pay you with carrots. You still have taxable income equal to the fair market value of the carrots. It's the same thing with bitcoins: the fair market value of the bitcoins is taxable income.
On the other hand if you receive cash as a gift or repayment of a loan or something like that, it isn't taxable, so it also would not be taxable if paid in bitcoins.
When you get rid of the bitcoins, either by selling for cash or trading for something else (carrots, gold, etc.), capital gains tax will be due on any gain in value.
Okay, so just the fact that it's not legal tender does not solve the problem. I am located in Spain.