What this means is that if there is a Resolver service available, clicking either the button to Install from repository or to Install and start from repository (circled in the picture below) will show a pop-up question asking if you want to resolve the selected resource and install its required dependencies.
Until the next full release this feature is available if you build from https://www.knopflerfish.org/svn/knopflerfish.org/trunk/.
In order to try this you also need to install an implementation of the Resolver Service. There is one available at org.apache.felix.resolver-1.0.0.jar.
To make things easier you can uncomment the following line in the init.xargs file in the osgi directory:
# Uncomment the following line to add Resolver support #-istart http://repo2.maven.org/maven2/org/apache/felix/org.apache.felix.resolver/1.0.0/org.apache.felix.resolver-1.0.0.jar