Haxorware source code (sb5101)

[Radiotubes]

none that i know of (shame)

<cough> Linux-mips
.
.
From the wiki:

Cable modem series includes BCM33xx SoCs, these SoCs are internally not very different from the BCM63xx SoCs, except that they integrate DOCSIS-related IP blocks instead of xDSL IP blocks.

BCM3348 combines an RF receiver with an advanced QAM demodulator, an advanced QAM and S-CDMA modulator/transmitter, a complete DOCSIS 2.0 Media Access Controller (MAC), a 200-MHz MIPS32 Communication Processor, a 16-bit, 100-MHz SDRAM Interface, 10/100 Ethernet MAC with integrated transceiver and MII Interface, and a USB 1.1 controller with integrated transceiver.
BCM3349 combines an RF receiver with an advanced QAM and S-CDMA demodulator, an advanced QAM transmitter, a complete DOCSIS 2.0 Media Access Controller (MAC), a 200 MHz MIPS32 communication processor, a 16-bit, 100-MHz SDRAM interface, 10/100 Ethernet MAC with integrated transceiver and MII Interface, and a medium-speed USB 2.0 controller with integrated transceiver.
BCM3368 uses the MIPS32 300Mhz Viper core and also supports the DOCSIS 2.0 standard, it combines a DDR-RAM interface, 10/100 Ethernet MAC with external switch support, an USB 2.0 controller with integrated transceiver and optionally 2x FXS ports.

You probably have to write some of your own stuff the make it work. It's open source