These are cheap hacks who want to make a quick buck off the App Store.
I dont exactly like the company, But I want to point out that trundle is free, so I really dont understand this...
They're making money through in-game microtransactions for extra content, so you can consider the "free" game kind of like a demo, to hook people in to buying the extra levels.
I have to say, after having just downloaded this and played for a bit, it does feel like a shameless copy of NightSky. The silhouettes, the sunset in the background, the ambient music, physics based gameplay with a ball rolling around. Even the curly trees which move around like they're alive, which can be seen at the ~20 second mark in the NightSky trailer. I have also been lucky enough to play NightSky at an art Gallery in Melbourne, and there are no significant gameplay differences (other than NightSky's being infinitely more refined, and far greater music).
I really think Nifflas should pursue this legally because his work is being copied, money being made with his ideas.