I just upgraded to 6.1.3, and now I am receiving a license violation. Looking at the past 30 days, I have never gone above 200MB/day, and only once touched 30% of daily license quota. I have one pool warning and one pool violation, with a "correct by midnight" message. Today's percentage of license quota sits at slightly over 10% as I type.
One problem that I faced when first using the free licence was that Splunk was indexing (and more to the point re-indexing after rotation) its own log files. This meant that there was growing input day-on-day. When using an Enterprise licence this problem never becomes apparent, because the Splunk logs are a tiny drop in the ocean, but when using the free licence it can take a significant bite out of the available throughput.
Very strange. Today the license violation was downgraded to a warning, and everything is otherwise working.
Splunk's internal logs do not count against the license (free or Enterprise).