IMSLP stands for the International Music Score Library Project and was started in 2006. The logo on the main page is a capital letter A. It was taken from the beginning of the very first printed book of music, the Harmonice Musices Odhecaton. It was published in Venice in 1501 by Ottaviano Petrucci, the library’s namesake.
The IMSLP/Petrucci Music Library is currently owned and run by Project Petrucci LLC, a company created with the sole purpose of managing this site.