To say it in simple words RSS is an XML based newsletter format which can be used to feed an RSS system like a reader or so. If you tell this reader where the RSS file is hosted (the URL of the file like https://forum.bandamp.org/audio_review.rss) then you can open a channel to this site and get the latest news on this reader. BandAMP generates two formats RSS and ATOM. And AWASU is a software developer for reading these formats.
Have a look at the review forum at the very end of the site. There you can see two icons that open an XML source. They contain the latest news.

So I wanted to figure out how this works and got above errors.

Maybe anyone can help me out?