First, I just wanted to clarify that all users who made more than 100 edits automatically received a 10-year contributor membership
How to make 100 edits without too big an effort and do something useful: search "1 piano" in the imslp search field. Some results will contain "Instrumentation 1 piano" or "Instrumentation 1 Piano". Edit the work page and change this field into |Instrumentation=piano and save the page. You will easily find similar cases that want a change.
Note that imslp's sentence is at the past tense. Mr Guo never said that users that would make more than 100 edits now would receive a free subscription, and for a good reason.
I waited a few months to see if the public uproar would get the Petrucci LLC admins to back off. It did not. As many others, I have been unconvinced by the arguments posted here to support this turning a community effort into a revenue-generating machine. The financial opacity of the whole enterprise is not the least of my reservations, although I also frankly hated their lame argumentation around the difficulty of running the service on a not-for-profit basis.
It all started with the potential difficulty of keeping IMSLP sustainable on the long term. Now, ironically, IMSLP may be still alive today, but the IMSLP community spirit is dying.
I suggest giving the admins still another month to turn IMSLP into a trustable organization. By may, with no apparent progress, it'll be time to move on. What has been done here can be done elsewhere, on solid bases (not-for-profit organization, elected board, transparent financial reporting). I'm ready to help.