I have some kombucha scoby that I haven’t been taking care of and has been doing it’s own thing for almost a year. It seems to still be alive. Is it still safe to use and will it still make kombucha?
I've been in the same situation (and am again... I'm a terrible scoby parent).
It's dormant and likely quite weak and/or imbalanced, but as long as it's not moldy or severely discolored, you should be able to bring it back. That said, you probably want to give it a boost. I usually buy a bottle of plain kombucha (GT's for me) and use that as starter tea instead of the ancient tea vinegar you have.
In my experience the well-controlled and cultivated commercial kombucha is pretty vigorous stuff, and a new, healthier scoby usually grows with the first batch. If any of your senses say yuck though, just let it go. These days you can get a new scoby fairly easily.
As always with kombucha, taste and smell are your best guides. A pH test kit is also your friend, with pH between 2.5-3.5 being ideal.