This priority queue is licensed under the MIT license. That means it's free to use in all cases: free for personal or commercial use, in free or paid software, open or closed source. No strings attached!
The only thing I ask is that, if you're going to use this in a commercial application, please email me and let me know, so I can brag about it (primarily to Jason, but also on my resume). You're also welcome to thank me in the credits :) However, neither of these things are strictly necessary.
And of course, I provide no warranty; so if my code blows up your computer, don't hold me liable!