I haven't actually used it yet but I don't think Zapk has a real reason to complain. First of all, it's a really old idea. I saw a version of rising lava back when terrains and interiors was a thing, so he can't complain about you stealing his idea. Second, it's not even the 'same' addon (similar but not the same), so he can't complain about you leaking his addon or something along those lines.
Also, you don't mind if I modify this a little do you?