1. It's explained in the README [1]. Tl;dr: Maiao is a "remote, sparsely populated volcanic atoll in French Polynesia"
2. I don't think so. The main difference from maiao to other stacked diffs projects is that it _progressively enhances_ GitHub. At the end of the day you just get PRs with branch #3 -> branch #2 -> branch #1 -> main. So, a bit of automation and rebases to do this. Because teams rarely can choose their forge, the intent is to not force org-wide change — e.g., change the VCS to jj — nor introduce more API/UI surface. You can be the only one doing stacked diffs in your team. Nothing breaks.