IMSLP rolled out a membership plan in December 2015. A thread with the rationale behind this change can be. This page includes a simple Q&A for basic questions regarding membership.
Q: Is membership mandatory?
A: No! Membership is not required to download almost all the files on IMSLP (except for very newly submitted files - see below), and you have access to all the features of IMSLP regardless. All Creative Commons licensed works are also downloadable without any waiting period regardless of your membership status. Also, files on the IMSLP regional servers in Europe and Canada are downloadable without any waiting period because these servers are operated by unaffiliated organizations that have chosen to simply collect voluntary donations through the server's landing page, without any membership required.
Q: What comes with a membership?
A: The membership includes the following:
Q: What a membership is not required for -
A: The membership is not required to:
Q: Who can I contact when I have membership-related issues?
A: Please send all questions to firstname.lastname@example.org, with your IMSLP account name (if any) and membership purchase transaction ID (if any).