There is an enterprise and a community edition of GDS. The community edition is free and available on our download center (or desktop, or github); Enterprise edition is licensed separately.
GDS community edition has all the algorithms, but has a four core limitation for calculations, which has significant impacts on performance for very large data sets (there are a few other differentiators, like RBAC integration and the availability of customer support). Here's the section of our docs that covers it: Introduction - Neo4j Graph Data Science
GDS uses the same GPL v3 license as the core database, as well.