It would be simple for yahoo serveers to use an Environment call to determine whether it's a browser environment or not and block any other app.
I think the incidence of people using the original app would be so seldom yahoo wouldn't notice.
forgive any typos.  Hurt my L middle finger today doing yard work and typing by  touch with 1 left and 5 right.
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Bob Bellizzi

Founder, Fuchs Friends ®
Founder & Executive Director, The Corneal Dystrophy Foundation