I think it's compatible, or at least it was last I checked.
As for making your own spells, you CAN do that, as the modder has released a modding API for this purpose. However, you would have to know some things about Minecraft Modding beforehand. I can't remember where it was posted, but there was an example spellcard up here somewhere you could use if you wanted to try it. I don't think anyone has ever tried to create a new spellcard though.