The document discusses the impact of migrating from an older Joomla! content management system framework version (1.0.x) to a newer version (1.5.x) that was rewritten to be fully object-oriented. It outlines several key impacts such as requiring a new support model, updated documentation, and potential need to rewrite some extensions. It also provides guidance on when and how to perform the migration including using available migration tools and treating it as a project.