Common current limit resistor for multiple LEDs?
Absolutely, this is perfectly fine. In fact, I'm doing the same thing in a project on my workbench right now.

If this was not good practice, you could not really use a LED matrix. There is no way to add a resistor to each individual LED:



As Arsenal points out in a comment, you don't even need a resistor, if you actually have a current source. Just set the current to whatever current you want through the LED. The resistor does absolutely nothing here except wasting heat. If you do this, however, I suggest that you turn on the transistor before turning on the current. Otherwise, the current source will try to push current somewhere, and hopefully hit a ceiling before it finds a way.