The ones provided with tinyboard, yes. But the additional ones from mlpchan have no license notice on top of the file.
By default, the copyright say that a script file is proprietary. If not, it must be under some kind of license. So, even if the js is perfectly readable and easily copyable, I don't exactly have the "right" to use them without asking first.
If they truly are open-source I would be very glad. I stay here for a confirmation from an admin. BTW, on top of using them, I'd like to release them with a GPL license, if that's ok. And of course a copyright statement linking back to you.