Make an app for a decentralized protocol, add some polish and maybe give something away with it which is cheap at scale (storage, bandwidth) as the loss leader and establish dominance.
E.g. TCP/IP is open; that doesn't make the Internet and Web open.
Open formats and protocols can serve as monopoly-enabling catalysts.
Could copyleft protocols be a thing?
We don't need copyrighted protocols and APIs.
We just need to mandate the basic / baseline technology. External File System that is supported everywhere ( ExFAT ? ), PDF, Word, Excel / Spreadsheet, Archive Files, Photo/ Graphics, Audio and Video.
Unfortunately I dont it will ever happen. One being goverement doesn't think like that. Two even if they do they dont know which one to pick. And three since they cant pick anyone they will decide to make their own.......
Right now I really wish we could create something on top of the soon patent free AAC-LC and H.264 Video Codec.
Ideally peer-based but I know federation is much more popular and that can work also.
But it's not just the fact that they leverage open software to build their closed systems, it's the large networks and marketplaces they have. The only way to compete with that is through decentralized systems. Which (despite the connotation of the name), are the best approaches for creating large scale, open, holistic networks.
Moving to decentralized protocols also means it is harder to dominate with one piece of software. Ideally the protocols are in some kind of protocol registry so they can evolve freely.
But on some level I believe that some entity like a government needs to mandate this. Although I know there are many people who are philosophically against governments or practically against them due to their track record of being generally awful. But at some level you may have to force people to cooperate in some basic technical way in order to avoid the technopolies.