[bdamm]

Yeah, but the original teams that designed or built the building are long gone, and in many cases the tenant/remodel work can happen without any of the original blueprints. Buildings are meant to be modified, and this is why we have building codes, subfloors, ceiling tiles, etc. In commercial software, the startup hurdle is so great, that it usually means only a team that is contiguous with the original construction team can economically extend the original in a meaningful way.

Open source requires a different way of thinking about it; not all software can be open source. Not all buildings can be raised like a barn. In fact there is very little in the construction or civil engineering world that matches what happens in open source software.