It's free at the moment, so feel free to try it. We will announce pricing and licensing in advance, so there'll be enough time to decide whether or not to keep using the tool.
So I try, and I like and I get used to it and then they start with "Oh you wanted to use that one really useful feature, That will be $5000 extra. Oh, you're running on Solaris, that will be $10000 extra. Oh you have more than 2 CPUs, that will be $20000 extra. Oh you want to use it Thursdays as well, that will be $30000 extra".
So now I never ever try software until I've seen a complete price list.
Wallaby.js will be less expensive than some similar commercial solutions for other languages.
In any case, feel free to sign up and to receive the pricing info as soon as it's available.