(Current work in progress)
Currently, the Core jar is ~247K, and the Gems jar is ~112K. The distribution zip contains all jars and documentation.
If you use Maven as the build system (or one that is compatible with the Maven Repository), you can declare dependencies as
org.picocontainer picocontainer[-gems] [version]
specifying the version. Declaring this dependency will pull in all other required dependencies (ie transitive dependencies). Note that PicoContainer core artifactId is simply "picocontainer".