They also showed me the Wondercab, an open-source arcade cabinet design

Does anyone know what they mean by open-source arcade cabinet design? I went to the link expecting plans/instructions to build one, but there's nothing of the sort there. The RCade cabinet even appears to be based not on the Wondercab's design, but on the Taito Gameroom classics cabinet...

The link: https://www.deathbyaudioarcade.com/wondercab