Yes it is a full instance. In that context. Splunk release the full package. It will give you 30 days on the license then you need to either allow it to roll over to a free license (which doesn't have certain functionality such as user credentials and a few other bits - all of which is documented), or buy an enterprise license.
You can add plug-ins such as Hadoop, as you indicate. There isn't a Hadoop Spunk version if that is what you mean. It's a Splunk instance to which the Hadoop plug-in has been installed.
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