It sounds like a 3-6 month, 3 person project to replicate with modern tech. I think all of the pieces of a Palantir-like system exist with open/free alternatives, but nobody has just bothered to write the glue code to make it happen.
This makes me wonder at the ultimate utility of the particular shape of a Palantir system if nobody else is bothering to do it in quite the same way.
It's probably some combination of PostgreSQL (plus PostGIS) + Elastic Search + Neo4j for the storage tech, pick-your-web-framework for the server-side, D3.js + some mapping library for the front-end and have all the major pieces. A few months of glue code and CRUD writing and it would be done. I'd definitely welcome a quick-to-deploy open/free alternative.
The real money is in the integration, ETL, ontology consulting service bit and so anybody could really build a company around that stuff.