Basically, there is a Linux program that plays the mp3z files.
According to one of Kobo's developers, it was intended as a quick and dirty hack when testing sound output and was never intended for public use.
As for the interactive question and eInk, you seem hung up on:
Here's a quote from Kobo's epub spec page which still applies to their eInk platform:
Quote:
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Kobo’s eInk and Desktop platforms have limited support for JavaScript, and do not support interactive JavaScript elements. EPUBs with JavaScript should contain fallback statements.
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Read-along is implemented using SMIL which again is not supported on Kobo's eInk platforms.