The trial was based in Brighton and used Linux software and an software defined radio (SDR) to broadcast DAB signals in the Brighton area, though the trial was only low power (the output of the SDR was set to 5mW) a signal could be received over 7Km away. There was also no detectable interference to the BBC local DAB multiplex which was around 3Km away from the trial transmitter.
The trial was carried out privately under Non-Operational Test and Development licence issued by Ofcom.
The full report is here, Ofcom doesn't endorse any software or hardware used, but the report contains references to all the hardware and software used.
Initially the trial was conducted using 2 laptops, but the software was integrated on to a single (rack mount) PC running xubuntu. It would also be possible to run at least some of the software (multiplexor etc) on a RaspberryPi.
Maybe this will lead the way for other Ofcom 'approved' trials such as running lower power GSM networks also using open source software.