If you follow the download links from the download section at openRDF.org you'll find that there are a number of different files that you can download. Which one you need depends on what you want to do with it:
openrdf-sesame-(version)-sdk.tar.gz.
This is a GNU-zipped tar archive of the complete binary version of
the Sesame SDK. It includes all the Sesame libraries packaged as
jar files and a set of Web Archive (.war) files for easy
deployment of Sesame's Web applications (see Chapter 6, Server software installation). It also includes
documentation (such as this user manual, and the API JavaDoc).
openrdf-sesame-(version)-sdk.zip.
This is a zip archive that has the same contents as the tar.gz
file mentioned before.
openrdf-sesame-(version)-onejar.jar.
This is a Java Archive (.jar) file containing all the relevant
Sesame libraries. The main purpose of this jar file is easy
inclusion of all Sesame components when using it as an embedded
component/library in your own application: you only need to add
this one jar file to your classpath and you can start programming
against it.
Apart from these binary downloads, Aduna also offers the Sesame libraries as maven artifacts in a maven repository. This maven repository is located at http://repository.aduna-software.org/maven2/. Developers using maven can use this repository to automatically resolve library dependencies and to get the latest released versions of each library. For instructions how to use the maven build system, see http://maven.apache.org/.
Sesame's source code is available from Aduna's Subversion (SVN) repository:
https://src.aduna-software.org/svn/org.openrdf/.
There is an SVN Web Viewer available as well at
http://src.aduna-software.org/viewvc/org.openrdf/.
Source code for each release is located in the
releases directory, the development version of
the code is in the projects directory.