This is a Karaf feature repository containing Akka features and dependencies. The releases are published in Bintray Maven repo here: http://dl.bintray.com/jarimatti/maven
See the Karaf documentation on how to add the Maven repository to Karaf repository list. After that install Karaf features repository and sample features with following commands in Karaf:
feature:repo-add mvn:fi.jarimatti.karaf/akka-features/0.0.1/xml/features
feature:install akka-osgi
feature:install akka-http