FYI - this is a VC backed project.

Expect this to become a paid offering at some point.

We do have a paid offering. Basically it's free on Linen's domain for public communities and we let you host on your domain like: https://archive.pulumi.com/ https://linen.prefect.io/ https://slack-chats.kotlinlang.org/

And you guarantee in writing that this pricing structure will never change?

If you want you can just host your own no? It's open source: https://github.com/linen-dev/linen.dev