I downloaded these a few weeks ago, and in the Readme it says:
These shaders are open source. Feel free to distribute them, modify them, etc., just don’t charge money for them. They require Poseworks’ pwToon which is available at DAZ3d.com. (pwToon is NOT open source!)
In this case only, it seems OK, but that is unusual in my experience.
Edit: Never mind. Confused them with the pwToon shaders in the store. The paid ones. Though, the fact they’re called pwToon shaders does leave me a little concerned about exactly how legitimate they are. If they’re based off the original pwToon shaders, but can be used without buying them, then I’m pretty sure that would be a EULA breach.