For now the Splunk jar is available on spring’s maven repo - http://repo.springsource.org/simple/ext-release-local.
The latest 1.0 release of Splunk SDK for Java can be added as a dependency in your project’s pom as follows:
<dependency>
<groupId>com.splunk</groupId>
<artifactId>splunk</artifactId>
<version>1.0.0</version>
</dependency>
Of course, you will need to add the above repo to your list as well so maven knows where to look for this artifact.