I haven’t seen an official comment on this, since May:
That said, Open Source For Good is a nonprofit (so is FCC itself now). Listed under the Open Source For Good section is a list of ongoing projects. The idea here is to create free, open source tools and utilities that are designed for the needs of nonprofits in general. Rather than making custom web applications for individual nonprofit organizations (something that requires a crazy amount of man hour overhead and logistical wrangling), Open Source For Good can offer tools that would normally be expensive or not well suited to nonprofit needs.
As for the “Claim your full stack certificate” link, if I had to guess I’d say that there probably just didn’t seem to be a great place to put it on the map right now. If you want to search around in the GitHub repo, I’m sure that you could find an Issue that includes the discussion of how the Nonprofits section was modified.