The requirement of an actual provider of related posts puts this plugin in a significant disadvantage as it will (and has) break with each time the dependencies break due to plugin updates. Sorry but this is a very poor design decision which overshadows all the goodness.
We are working on an upgrade for the plugin and will try to incorporate the related posts fetch functionality within “Related Posts Slider”. Probably the next upgrade will have that functionality. I know the dependency especially on YARP is causing so much concern. Till the next upgrade, it is recommended to use “WordPress Related Posts” plugin on RPS settings panel and install that plugin on WordPress as well.
The next upgrade is scheduled to release by first week of January, 2012.