https://atproto.com/guides/applications
You can use atproto to build other federated applications.
Just because one implementation of atproto (bluesky) doesn't have feature parity, doesn't mean it's a fake federated protocol.
'actual fediverse' and 'bluesky fediverse' doesn't make sense as a comparison.
It's more like, ActivityPub vs ATProto.
https://github.com/bluesky-social/atproto
Bluesky is just one implementation of the protocol, that implementation happens to have a lot of steam, but it's not fake or anything.
For real open source projects, it's a lot of the time not nerds working for free.
All your favorite frameworks and libraries are often developed in house at big companies (angular, react, vue, tensorflow, Kafka, pytorch, k8s, Jenkins, and many many more).
And even then, much of the development on them is done by people who are getting paid to use the frameworks at smaller companies.
There are tons of examples the other way too of course, but even the Linux kernel is mostly corporate commits, Google, Huawei, Oracle, and others.
This isn't inherently bad, but it's not as cut and dry as people make it out to be.
I want to add, that language development is also often done by companies. Today for example is a Mozilla thing, and while a non profit, the devs aren't working for free.