Through some reverse engineering, the two developers produced firmware for at least three Broadcom wireless cards (4306, 4318 and 4320) and announced their release under GPLv2. They based their work explicitly on their own experience and assembler/disassembler software developed by the b43 community "as a starting point to implement other MAC [Medium Access Control] algorithms for research purposes." It can spare Linux users who use wireless cards with the chips from having to access the Broadcom website.

Previously users needed to run a special b43-fwcutter (firmware cutter) script that extracted the firmware from the website. Broadcom has recently supported Linux only via proprietary drivers without providing free access to the firmware. The open drivers from the Open Firmware for WiFi (OpenFWWF) project are meanwhile still based on the initval data from Broadcom's firmware. Users extract this data by following the b43 driver installation process.
The OpenFWWF project firmware is available for download from the University of Brescia (Italy) website. A few caveats: unsupported in the firmware are RTS/CTS handshakes, hardware cryptography acceleration and dot11 quality of service (QoS).

Most users will have to wait some time before the drivers go into a distro. The b43 tools to compile the firmware are available here and the source code here. The project website also shows how to use the downloaded firmware.