Legally though, just because one person's proprietary work relies upon another person's proprietary work, doesn't mean it suddenly becomes open source or public domain.
Honestly I’m not surprised. The prior work could be argued as being fair use of the Tetris copyright. It certainly isn’t stealing any market from any official licensed Tetris products or services. Morally, I can find it very easily defensible.
This “Lovetris” work is a blatant copying and republishing of someone else’s proprietary work effort with no permission. Morally, I don’t see this as an egregious abuse, but I can see why this community would object to someone not acting in the spirit of open source licensing.
Legally though, just because one person's proprietary work relies upon another person's proprietary work, doesn't mean it suddenly becomes open source or public domain.