Low count suggests that the project has an intentionally built core and doesn't undergo churn or feature creep. It's also a good sign that commits per week have decreased substantially over time.
Contributions being mostly from a single developer lends further credence to that idea, because it implies everything is fueled by one person's relatively opinionated vision and taste.
A single(-ish) author is the strongest smell for a library. I've been burned countless times by a project's "BDFL" moving on to something else. Sometimes a new maintainer will take over, but it's rare.
Low commit count also suggests unresponsiveness to issues that are filed, especially for a TypeScript or JavaScript project.
This thread single-handedly convinced me not to start a Solid project.
Low Commit count suggests nothing other than maybe lower traffic. I've been able to keep issues the main repo under 50 issues most of its life. I admit work towards the next major version has let this slip upwards. Also effort is split among multiple repos. Repos where I'm far from the biggest contributor. The core is small and manageable. Which is a good place to be 9 years in (7 of those open to the public).
SolidJS (Ryan mostly) is very responsive, so the low count is more a sign that there are not many issues which require code changes in the first place. Which is good!
>Sometimes a new maintainer will take over, but it's rare.
SolidJS really doesn't need a full-time maintainer at this point. One or more community members fixing severe bugs and keeping it up to date is plenty enough.
Contributions being mostly from a single developer lends further credence to that idea, because it implies everything is fueled by one person's relatively opinionated vision and taste.