If there was a DIY dish with open-source firmware, could it access starlink network? It's 24/7 from the sky like GPS. Just how to receive those signals? How does it differ from GPS?
Discussion
You don't just have to accept signals. You have to send signals and have the network accept them. Since Starlink wants to get paid, if they have the most basic level of competency, they'll have their network set up to require authentication, so they'd just refuse to carry your traffic.
Plus, they don't just broadcast the whole internet all at once, so even if you could just passively receive signals in your area, you'd have no way to make requests, so you couldn't direct it to send you what you actually want.
Ultimately, the issue isn't the endpoint Starlink kit. It's the entire rest of the network it depends on. The rest of the network won't play nice until you pay up, so even if you have 100% full control of the kit, you can't make the satellites serve you as an accepted network participant.
Centralized & permissioned as fu*k
No different from any other widespread network, unfortunately. The only public attempt to rival them has been mesh networks, but I've never heard of one getting very big. Even if you managed to cover a while city in a mesh network, how do you get a high bandwidth connection to another city with a rural gap in the middle? You'll get to the point where wireless solutions won't work, and you'll need a physical connection, but then who lays the wire? How do they get permission to lay it since they can't just buy a 3 foot by 100 mile stretch of land for the wire to sit in? Resolving all that in a capitalistic society inevitably leads back to corporate ownership of, at a minimum, crucial connections in the network.