"I respect the original creators Igor Pusenjak and his brother for their great work."
Uhhh no you don't. This is textbook copyright infringement. You can't copy without permission and then claim you respect them. That's not how things work.
In any case, I'll invoke the maxim "imitation is the highest form of flattery" as an argument. Why do so many people new to game development make (and are encouraged to make) Pacman clones, Snake clones, Tetris clones, Asteroids clones (one is still on the front page with no shouts of "copyright infringement!!!"), etc.? Because they're fun, respected games that are easy to clone with modern tools. This game is no different apart from not having as many people thinking it's a good game.
This platform mechanic is over a decade old (and mechanics can't be copyrighted anyway), the platforms themselves are probably too simple to qualify under copyright. (The alien sprite you might have a better argument for, but that's very easy to change and if I were the author I'd do that not to play it safe but because the standard alien doesn't look very good.) The only thing I would suggest the author really bother changing is adding the word "clone" or "recreated in HTML5" to the title of the project even though that information is already in the description.
Fair use? For your own sake I highly recommend you take a class on copyright law. I don't say that to be mean. Copyright law is both complicated and important. But if you think that's fair use then you risk fucking yourself or your employer.
I can imagine it being successfully argued the other way by a persistent prosecutor. But considering all the fair use tests I think a reasonable interpretation is to let it be. Of course US law and judges are anything but reasonable a lot of the time, and if someone is looking to fuck you over there are plenty of ways to do so. I'd wager there are more than one patents being violated by this game (and the original it was cloned from) for instance.
The other consideration is that the developer is in India, which unless he's doing things on the scale of Dotcom allows him a "come at me bro" attitude if he felt like it. Fortunately he seems like a decent fellow, so it's a non-profit learning exercise of something with a lot of prior art in terms of gameplay, it's not a complete clone, and I doubt it hurts sales of the original (which he links to).
Uhhh no you don't. This is textbook copyright infringement. You can't copy without permission and then claim you respect them. That's not how things work.