The original version is a small clone of 1024, based on Saming's 2048 (also a clone).
2048 is licensed under the MIT license.
Gabriele made this in his spare time, and it's hosted on GitHub (which means I don't have any hosting costs), but if you enjoyed the game and feel like buying him coffee, you can donate at his BTC address: 1Ec6onfsQmoP9kkL3zkpB6c5sA4PVcXU2i.