Do I need to ask permission in order to use it under under a Libre Creative Commons license which allows commercial usage alongside sharing and remixing as well as the ORC License, which is the new spiritual successor to the OG OGL 1.0a, which also allows the same stuff too I mentioned. I'd so live to mix this supplement with my own remix of the Black Flag RPG SRD from Kobold Press, which is under the ORC License.
I would put this under CC-BY-4, so you don't need to ask permission (but I certainly appreciate it!), just credit me somewhere for it (there's guidelines with that link if you want to get really official with it).
However, if you are wanting to use it to build your own monsters to put in your work, then it's not really my work at that point.