The link from the library site might be the "official" MIT endorsement, but the profs in music at MIT have been using the works in our classes since day one of IMSLP. What a great project. Also, the MIT OpenCourseWare project is linking to IMSLP scores where available for pieces used in MIT courses, so that's a second endorsement.
Just uploaded my first set of PD scores (finally giving _something_ back); thanks for making it so easy! Agreed that the Wiki format was the stroke of genius. That plus the GNU Free Documentation License which lets users know it's worth our time to contribute.
Visiting Assistant Professor of Music