You are not missing it -- it does not seem to be published yet. The site says open source but from the updates page it looks like the hardware design files and SDR software will ship alongside the physical product when it launches. This is pretty common with open-source hardware projects: the design is open but the repo appears after the first production run, partly because the schematics and firmware are still being iterated on and partly because publishing incomplete designs invites issues before the team is ready to support them.

What I find more interesting than the license question is the software side. They mention a pre-loaded SD card with SDR applications, which probably means GNU Radio or something built on top of it. If they release the beamforming DSP pipeline as open source, that is genuinely valuable -- most phased array signal processing code is locked behind defense contractor NDAs. Having a reference implementation that people can study and modify on commodity hardware at the 399 dollar price point would be a significant contribution to the SDR community regardless of when the repo goes live.