FWIW - Redpanda open sources their core product - https://github.com/redpanda-data/ while WarpStream keeps their core product proprietary - https://github.com/warpstreamlabs
I can see the source code of Unreal Engine too. Does that make them "further into the open source world" than WarpStream too?
I don't have a horse in this particular race but WarpStream's blog post is a lot more charitable towards the project in question, and the open source world in general, than Redpanda's.