Resembles Arduino IDE so much I think they may be related?
That's because they are. The processing IDE written in java is what the arduino folks ported over for use as the IDE for the arduino and that's why loading the arduino IDE distrubution onto one's PC one ends up with having Java installed even though we write your sketches in C/C++ to have compiled and uploaded to the board. The Arduino platform is a soup mix of various other independent open source projects combined into the arduino open source platform.
I guess on could say that the Arduino project is a project based on other projects. Or one could just call it a mutt.