For an overview of the membership plan see IMSLP:Membership Q&A.
For more information on the reasons behind this change, see this announcement on the IMSLP Forums.
Please note that some newly-uploaded scores may only be available after a day or two to non-subscribers.
I am currently studying Music Education and am very interested in Conducting. I joined IMSLP to help tidy up scores, and in some cases re-score public domain tunes into flexible ensembles/instrumentation.