Textures are nothing, but a outright code rip is a big something. And I believe @
Vazkii has quite a bit to say on this topic. I know that IC2 is dead, but that doesn't mean it's okay to rip code from a mod to make your own, open source or closed source, a modding community does not stand for this shit. Ideas are cheap and that's fine. Textures are easy to make. Models, well, not a good thing to take, and code? FYAD if you steal code. Ask if it's fine, even if it's open source.
Maybe it's because I'm from a modding community that is based upon open source code, I know that one always asks first. Many people in the Minecraft community have never modded. I have, but for TES III, TES IV, and considered getting into modding for TES V, so yeah, I know better then many Minecraft players.
So unless you have modded, you aren't in a position to say what is or isn't fine. And even if you have, you're still wrong to think that all that was taken was the idea.