Introducing VegaFusion 1.0: now a Hex OSS project

Hex has officially open-sourced VegaFusion, making it a Hex OSS project. The project has been re-licensed to BSD-3 from AGPL to encourage broader community adoption. Version 1.0 of VegaFusion is released, incorporating work done to back Hex's new interactive chart editor, including improved support for Altair. This allows Altair users to leverage VegaFusion for pre-evaluation and optimization of charts without Jupyter Widget extensions. Future work includes aggregate pushdown to SQL.