Broadcom are employing Eric Anholt to build a fully open source, upstream DRM/Mesa Gallium driver for the VideoCore 4 (https://anholt.github.io/twivc4/) and assorted Raspberry Pi hardware.

Now that's hardly a big focus of Broadcoms business but you can pretty much run a fully open source GPU accelerated Linux userland on the Raspberry Pis with those efforts.

Bluetooth and WiFi is proprietary though, if I remember correctly. And that is what Broadcom makes money with.