Is my pizza dough still good?

It has turned into a sour dough, there is allot of sour dough starter recipes. I say bake some and see if you like, I have starter siting in the frig, and use it all the time, there is a web site pizza making.com, and a good dough recipe has aged dough

It is past its life. The yeast has fermented and basically if you use it it will have an off flavor as well as not rise for you. When I make pizza dough I increase the yeast by 1/2 times the recipe, portion in 12 ounce balls wrap tightly and freeze. Pull it out in refer the night before and by the time its time to make dinner its ready to toss. Freezing does kill some of the yeast so that's why I add that extra. Results in a nice bready crusty pizza dough.

Pizza dough begins to ferment in the refrigerator after a couple of days. I think that the taste will be compromised even though it would not be harmful if you ate it.

Definatly not! You should never eat food thats been opened after 4 days, and that should be the max. Even if its refrigerated. The only way to keep food like that safe is to keep it frozen till your gunna eat it. Other than that it should only be left for a couple of days.