The soundtouch web api which is what was "open sourced" was already an existing thing for a long time. You just had to access it from the bose developer portal I think. I don't think anything actually happened here. I'm so surprised that HN is excited about this story because nothing seems to have been released.
This is making them controllable.
The headline may be inaccurate, but I'm not clear on what source code you'd even want. To the firmware do you mean?
A documented API seems like the most useful option here.