I actually kind of got it working. Splunk will ingest most log files and with an additional so called Add-On, it will ingest graphite formatted logs. I was able to configure my Harvest box to send performance metrics to Splunk. It's not pretty, but I may be able to make some use of it.
For my next challenge, I wanted to take the ready made NABox virtual appliance to get all the goodness of a polished package which my customers like, and try to siphon off an additional log stream to Splunk.
Accordning to the Harvest documentation, this is possible using "Graphite relay".
I'm reading the Carbon documentation link , it it speaks of a releay-rules.conf. Seems easy enough, but the same page mentions the main carbon.conf file, which also should be located in /opt/graphite/conf. There's no carbon.conf file in my NABox. Am I missing something here? NABox is working fine as far as I can tell.