Here is the full information regarding downloading Deltarune on PC.

Deltarune is a free game, but only Chapter 1 & 2 are currently available for free. Future chapters (3, 4, 5) will be released as a paid package. There is no official "full game" download yet. Official Download Sources (PC) You should only download the game from official sources to avoid viruses or fake files. The official publisher is Toby Fox .