I modified The_Evil_Pickle's various tiles mod and added many things, such as better textures and more uses for lava. However, one of the uses is for power, in a very similar way that this mod introduced it. I had a clear idea and was close to done when this mod came out, so I didn't use any material from it, but licensing scares me. Can I post it, or should I keep it private?

Provided you have none of my assets or code, you are free to release your mod. My license only affects my creations.

That said, I do recommend distinguishing the mod in some way; two identical mods - or one entirely encapsulating another's functionality - is rarely desirable.