This question was better directed toward Customer Support (CS) and The Community should have suggested as much. Given that Win2000 OS is not supported, CS is in a better position to make a 'best fit' recommendation.
"Splunk provides previous releases for customers that need access to a specific version. These versions are fully supported for customer's with a current enterprise license and support agreement." -- http://www.splunk.com/page/previous_releases
Discussion:
There is a persistent characteristic in the IT industry, that many companies continue to use 'unsupported' hardware and software long after the product owner, some by choice and some through insolvency, discontinues meaningful support. Industry can be found using systems that were provisioned as far back as the mid-80's. There is also the secondary marketplace for core infrastructure and specialized technologies where 'obsolete' is all that is available for entry-level entities and those operating on a tight margin. The CompTIA A+ Certification reflects the persistence of 'obsolete' technology.
If Splunk indeed refuses to, "...write or support software for obsolete operating systems..." then they risk neglecting a significant, though not necessarily majority portion of the 'big data' market place.
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