You can write programs that use Hopsworks in any Python, Spark, PySpark, or Flink environment. Hopsworks also running SQL queries to compute features in external data warehouses. The Feature Store can also be queried with SQL.
There is REST API for Hopsworks that can be used with a valid API key, generated in Hopsworks. However, it is often easier to develop your programs against SDKs available in Python and Java/Scala for HSFS, in Python for HSML, and in Python for the Hopsworks API.