The Eclipse Theia platform is consumable in the form of npm packages (namespace @theia).
See also the release overview page for details about specific releases.
The Theia IDE is an IDE application built based on the Theia platform. For more information about Theia IDE, please see here. Below are direct links to the latest version.
You may need to right-click on the wanted package and use "save link as" or such.
The Theia IDE is also available on snap.