I get what you mean and I think the other guy was indeed misleading about this, but there really are lots of contexts where subscriptions are free. In the classic postal sense newsletters are mostly free (and yes, mostly spam), when a program "subscribes" for events from another program there isn't cost involved; and most importantly youtube channel subscriptions exist.

I also had the impression he implied paying for lichess, but technically the word subscription doesn't necessarily have that meaning in our current time any more.