Keyboard Backlight Limiter is now Dim Keys. Same app, same settings — the name is what changed.
Your settings carry over untouched. The brightness ceiling, the ambient sensitivity and Launch at login all belong to the app's identity rather than to its name, and that has not moved.
Dragging the new app in does not replace the old one. A renamed app lands beside its predecessor in Applications rather than on top of it, and both copies drive the same keyboard backlight — so left alone they work against each other. If the old copy is still your login item, the one that wins on the next boot is the one you are no longer looking at.
Dim Keys offers to clean that up the first time you open it. It quits the old app, moves it to the Trash — not a permanent delete — and re-points Launch at login at the new app for you. Prefer to handle it yourself? Choose Not Now and drag the old app to the Trash; the offer will not come back. Fresh installs never see any of this.
If you are updating from a notification, the banner will still say "Keyboard Backlight Limiter". It is posted by the copy already on your Mac, which predates the rename. The download is called DimKeys-1.2.0.dmg and it is the right one.
Universal, signed with a Developer ID and notarized by Apple, so it opens with a double-click. macOS 13 or later — though everything has only been developed and verified on macOS 26, so anything earlier is genuinely untested rather than merely unsupported. If the app reports that no keyboard backlight was found, please open an issue and say which macOS version you are on.