This extension was part of Blender 4.1 bundled add-ons. It is now offered as it is, with limited supported.
IMPORTANT: Add-on now uses new, better data-structure that no longer depends on exposed custom properties which were easy to mess up. Because of that if you have files saved with unapplied Bool Tool modifiers you need to enable "Versioning" in preferences to update your files to new version of add-on.
Read more detailed changelog here: https://github.com/nickberckley/bool_tool/releases/tag/v1.0
This extension does not require special permissions.