These notes are provided for historical reference purposes only. Version 62 and later do not use this method of integrating with Spotlight, and instead use a special mdimporter to intergrate - a much safer method.
When the SpotMeta Spotlight extension is installed
Every time the SpotMeta Agent runs (every time you log in), the installation status of the Extension is checked. Apple may update the mdimport file with Software Update.
If a change is detected, you will be asked to reinstall the Extension. In this case, another copy of mdimport will be available in /Library/SpotMeta/Original so the changes made are always recoverable.
The installer is extremely careful to always do the right thing. What's in the executables is checked every time before every operation to ensure that you don't lose anything important.
It even includes a secret way for Apple to inform SpotMeta that it supports the SpotMeta extensions natively. Maybe in Mac OS X 10.5?
During uninstallation, the latest Apple mdimport is restored to the original location. Copies of all the versions ever found, including the latest one, will still be available in /Library/SpotMeta/Original, just in case.

How SpotMeta helps you organise your files
Information for Advanced Users
SpotMeta is an Open Source project, licensed under the GPL.
See note about development status on the contact page.