Does Paligo use DITA?

As others stated, Paligo is based on the DocBook5 schema. As with the DITA schema, DocBook5 allows for the separation of content and formatting. Authoring tools that are based on DocBook5 or DITA all produce structured content using XML tagging. Content produced with both DocBook5 and DITA tools can support content reuse, variables, topic-based authoring, single source publishing, taxonomy, etc. I've used DITA tools in the past and currently use Paligo. I've found a lot of the feature set to be similar, although implemented differently.

No. It is topic based and uses the DocBook paradigm for its internal XML.

No, it uses DocBook, another XML language, which does most if not all of the things that make DITA useful to tech pubs groups.