There are some issues with this:
Internally the drip catcher tray is exposed to the air currents running through the compressor. As such, it will have dust, pollen, and general crud -- Pretty much what you find on your swiffer.
Sometimes these catch trays are designed cheaply, so the water doesn't drain until it gets to be 1/8 to 3/4" deep. So you have dirt soup. All kinds of stuff find this a happy place to live. (Wasn't Legionnaires Disease traced to mold in water in an air conditioner?) This damp tray of stuff is responsible for some of the odd smells that come out of an air conditioner.
Overall I would prefer to drink from a fresh mud puddle.
Could you run it through reverse osmosis? Yes. I'd want to run it through a good filter first to get out the crud. Indeed: If you know that there is nothing toxic on the tray liner (galvanized steel say) then filtering may be enough before UV treatment.
Also: The amount of water isn't huge. Not having lived with an air conditioner, I can't say for sure, but I'd be surprised it it were more than a few gallons a day. This is too much work to salvage a couple of toilet flushes a day in the cooling season. Direct the drain hose to your favorite tree.
For water conservation, you have much better targets:
- Grey water -- everything but the toilet and kitchen sink/dishwasher drain. This water is unfit to drink, and contains soap and dirt. Neither of these harm plants. It is quite reasonable to internally divert this, and either drop into a cistern that you use for watering in your yard, or run to a tiny wetland where it can soak into the earth.
Note that this process is trickier in climates where you have extended periods of frozen ground.
Addendum in response to comment:
For years I had a neighbour who, to save water costs diverted his washing machine through a 6 foot pipe to a pond which he then used for watering his garden. No problems were seen around the pond and I can testify that the garden produced wizard squash.
Observations of culverts where there is splashing on the water hitting the pond below: There are lots of natural soaps. 2-3 inches of foam below a culvert draining land that hadn't had a chemical sprayed on them in 10 years...