Currently the hadoop-hdfs jar contain both the hdfs server and the hdfs client. As discussed in the hdfs-dev mailing list (http://mail-archives.apache.org/mod_mbox/hadoop-hdfs-dev/201404.mbox/browser), downstream projects are forced to bring in additional dependency in order to access hdfs. The additional dependency sometimes can be difficult to manage for projects like Apache Falcon and Apache Oozie.
This jira proposes to create a new project, hadoop-hdfs-cliient, which contains the client side of the hdfs code. Downstream projects can use this jar instead of the hadoop-hdfs to avoid unnecessary dependency.
Note that it does not break the compatibility of downstream projects. This is because old downstream projects implicitly depend on hadoop-hdfs-client through the hadoop-hdfs jar.