Its not even a demo, you need another switch that has the full copy of the game to use the free software on your own switch. Its a multiplayer game that uses two switches, if you've ever had or played Pacman VS on the nintendo gamecube its the same game where three players control ghosts on the big screen(the gamecube and in this case the switch thats docked) and then one players plays as packman on the smaller screen (the connected gameboy screen and in this case the other switch in handheld mode). In the full version you can still play the game without having two switchs but you wont be able to play as pacman youll only be able to play as the ghosts and chase the pacman AI.
Heres what it looks like on the gamecube
Its the same game in Namco Museum, and this free software allows people to play the game without having to purchase two copies of namco musuem