RDF-Ext uses many libraries from the rdfjs-base organization. To simplify the usage, the factory handling is done for you. The features are available through the RDF-Ext factory.
The packages in the GitHub organization @rdfjs-baseopen in new window implement many basic features. They are factory agnostic and can therefore be used without RDF-Ext. But the usage without RDF-Ext is a little bit more tricky. That's why it's not recommended for beginners.