ToolJet is open-source - https://github.com/ToolJet/ToolJet

> Self-hosted Business & Enterprise plans only

(Windmill Founder here) Our workflow part is open-source so it's not 1:1 comparison

From the GH repo:

> You can deploy ToolJet on Heroku for free using the one-click-deployment button only until 28th November 2022.

Why the limitation?

Heroku removed their free tier.

There's also https://github.com/windmill-labs/windmill and https://github.com/activepieces/activepieces depending on which parts of retool and tooljet you care about.

Budibase is open-source, including the workflow platform which has helped accelerate thousands of workflows already:

https://github.com/Budibase/budibase

windmill.dev got linked in the Bun release thread earlier, and I think that looks promising. Haven't tried it yet.