Could the Voynich Manuscript be a private educational system?

[Linda]

But the question is the same - why did the author need his own writing system?

I see it as information that its reader(s) could use to recreate the information, on paper, to sell to others perhaps, that they didn't otherwise want anyone to have access to, the main copy of the information is thus protected from getting into the wrong hands. Like a built in copyright system.