My cat won’t, that’s a clue…
It appears to be water,yet I’m not sure…doesn’t hurt plants,comes from the air. I just don’t know…
I actually tried a (tiny) bit once out of curiosity. It had a plastic/oil flavor (the water drips out of a sort of filer), which suggests it’s not especially good for you. Maybe it has traces of PVC or something. In an emergency it could be a life saver, but otherwise your cat is probably right.
No. Rarely does the typical person clean out (i.e. sterilize) those collection pans. Over time, they become a breeding ground for microorganisms.
If 'ya boiled it, I’m sure it would be safe. But as mentioned above, without it, it’s full of nasty beasties, and probably a fair amount of dust, as the places those are usually put tend to be dusty.
As for the cat not drinking it, only the freshest water will do for an ordinary cat. They may “sink down the chain of quality” if they begin to get very thirsty.