I'm not sure if I answered your question or not?
Yeah I presume commissioned privately used / for later freely shared two-dimensional art is kosher.
... but of other forms of media for Touhou Project fanworks (animations, games, music) -- would other commissioned work done in the same manner as two-dimensional art fall under the normal environment of a commission (such as how the Sistine Chapel's ceiling was commissioned by Pope Julius II by Michelangelo; amount of involvement in the commmissioner / patronage is of course presumingly substantial).
Environment of a commission is normal: statement it is
not 'work for hire', that it is for commission, composer/writer/artist/whatever retains the rights to the work, the normal guidelines for fanworks of ZUN is otherwise met as if the patron/commissioner made it themselves, etc.
The question extends to almost all fanworks to kind of cover just about every possible imaginable situation for a person to commission a work (Hell why not, a fresco of Touhou fanwork on one's ceiling lol!).
I could imagine this being used for those that might be ... ballin' (but if you have that kind of money to
completely commission a work ... well ... don't think we have 1%/0.5%'ers in MotK? Bueller? Bueller?). But realistically, I'd expect the most common would be 2d/3d art and music arrangements.
Edit: Oh you researching lol. okay. ^^;