Currently there are client libraries for Python and R that can be used to develop against Dataverse APIs.
Because Dataverse is a SWORD server, additional client libraries exist for Java, Ruby, and PHP per the SWORD API page.
https://github.com/IQSS/dataverse-client-python is the offical Python package for Dataverse APIs.
Robert Liebowitz from the Center for Open Science heads its development and the library is used to integrate the Open Science Framework (OSF) with Dataverse via an add-on which itself is open source and listed on the Apps page.
https://github.com/ropensci/dvn is the official R package for Dataverse APIs and is available on CRAN at http://cran.r-project.org/web/packages/dvn
It was created by Thomas Leeper whose dataverse can be found at https://dataverse.harvard.edu/dataverse/leeper