I must admit that I have no experience with the LED matrix component, but as I understand that matter:
You will need an external driver for the commons (might be a transistor). GPIO pins are able to drive/sink up to 10 mA which would result in different brightness depending on the segments of the digit switched to "on".
Common anode or common cathode is then selected by the circuit that drives the commons and the polarity set for the segment driver.
The example shows all the commons hooked directly to the 7-segment LEDs. But doesn't make clear which are anodes or cathodes and both actives are high. After some messing around I found something that somewhat works but doesn't work well so I think I'm still looking for the right answer.
What I have set up now is:
8 LEDs, common anode connected to the Segment pin, cathodes are connected to 8 different Commons pins (yeah, that sounds opposite of what you'd expect but you can only set brightness on commons and I need to do individual brightness on each led).
Segments are active high. Commons are active low.
The intensity is not what I thought it would be. Maybe it's because there are 8 coms and the refresh rate is not great. I will have to try using an external clock and bump the rate.
I'm still hoping someone will have a good answer to how this component is supposed to be used properly.
The intensity is not what I thought it would be.
As I said, use a driver and resistors for the segments.