OnyX is the main application. The Maintenance and Deeper applications are parts of OnyX. Maintenance is similar to the OnyX Automation pane, and Deeper is similar to the OnyX Parameters pane.
Then if you use OnyX, the Maintenance and the Deeper applications are redundant!
There is a specific version of the applications for each major version of the operating system.
Use the specific version, and don't try to use a non-compatible version.
Read this software license agreement before using the software. By using the software, you are agreeing to be bound by the terms of this license.
OnyX is translated into several languages by volunteer users and some professionals offering services localizations.
Here are links to sites that would be useful to bookmark.
"Thank you" to them for their help during all these years.