You're not allowed to use resources (that means graphics, music, sounds
1, etc.) straight from an official game/data file
However, you can make your arrangements of the music, you can make your own sprites and drawings of the Touhou characters and sell those in a game you make.
Otherwise I'm pretty sure
Reitaisai wouldn't exist.
1 Unless a sound in the game is from a free soundbank (packs of sound effects), in which case get them from the soundbank along with many other sounds :V