Whenever I'm talking to people able making fermented beverages, many are very concerned about mold or harmful bacteria. I have heard of people even going as far as sending their kombucha samples to a lab for testing before consuming!
Generally speaking, with most fermentations, if it looks and tastes good- it's good. Food safety rules change drastically depending on where you are in the world. One cultures inedible, "rotten" or "dangerous" food, may be another's delicacy. Now with kombucha, you definitely don't want to mess around if you've got mold.
A kombucha scoby can go moldy if your fermenting conditions are unsanitary, you have forgotten to cover it with a coffee filter or clean cloth to keep out airborn particles, or if you divide up your scoby too much and then try and get a tiny piece to ferment a very large batch of tea and sugar (which is the mistake I once made and you can see the results below!)
That is a moldy scoby! Those little brown, stringyish bits you see on your scoby are not. Those are simply yeast. If your scoby goes moldy, do not drink the kombucha or reuse any of it's babies. You'll have to obtain a new mother from someone and start over.
If your scoby looks healthy and your kombucha tastes good- sweet, sour and pleasant- than it's good. No need to pay money to send it to a lab! After all, making it yourself is supposed to SAVE you money. Cheers!