No worries, you don't have to pay a cent. By adopting a word, you're promising to use it in conversation as frequently as you can to help save it from fading away. Turn up your sound to hear the pleas of these endangered words.
If nothing else, it's really interesting to scroll over the collage of words and check out what some of them mean. If you happen to find one that really jumps out to you, don't be afraid to adopt it. I'm sure it'd be muchly appreciated. <3