The Nice Thing About Standards
In Europe, the spectrum was sold to mobile phone operators on the condition that they use it to implement GSM networks. GSM is getting a bit long in the tooth, but at the time of deployment this was quite a novel idea. Previous phone networks had been based on closed systems. Each network operator would define its own standard (or have one defined by whoever manufactured the radios). There was no expectation that phones would work with other networks.
Gradually, GSM replaced the older systems in most of the world. This change was great for mobile phone users. When I visit a different country with a GSM phone, I can pick up a cheap pre-pay SIM and have a phone that works locally. The downside is that my phone number doesn't move with me. If I want to have my home network forward calls for me to a network in another country, I end up paying a huge premium.
Now, imagine what would happen if I just used the phone for data access. My IP address would change, but IP addresses were never meant to be used directly; that's what DNS is for. I could run a VoIP client on my handset, and no one would know which connection I was using.
I already do something like this with instant messaging. Sometimes I'm on my home Internet connection, sometimes at work, and sometimes using my mobile phone for access. But no one needs to know the details of which connection I'm using, because we use a standard protocol for communicating.
An open network would need these standards to be taken much further. The campus where I work has an "open" network. It uses Ethernet. Network access points are dotted around the place, and I can plug in a laptop at any of them. All that's required is that my machine support a whole stack of well-defined protocols. At the bottom layer is a set of specified voltages for ones and zeroes, then Carrier Sense Multiple Access with Collision Detection (Ethernet). On top of this is IP, TCP, and then protocols like HTTP. If I support all of these protocols, I can communicate with anyone on the local segment. If I support them and have my machine registered with the people who control the routing infrastructure, I can connect much further.
An "open" wide area network would need to be designed in the same way, with a mesh or broadcast topology for local connections over a standard protocol that prevented anyone monopolizing the (finite) available bandwidth, and a mechanism for routing packets over long-distance links that form the existing Internet infrastructure.