Earlier quoted context omitted.
The problem is GitHub spends on the order of $100m/year on providing free CI. Nobody else can compete with that. It's possible they could make it shit enough that a large number of projects will say "screw this we'll just pay for CI", but people really like free (and easy!) things so I think we are a long way from that point.
"Nobody else can compete with that" My laptop is on all the time, make a WASM slave and thousands of developers can give their CPU/Memory/Disk for build slaves. Like bitcoin mining, there could be some competition between 3 parallel builds to pick the winner if the output is the same.
WASM isn't a magic bullet for sandboxing. CI environments assume a full Linux. So you need to either ran a VM (with the attack surface that implies) or a write an x86 emulator in WASM (which would be very slow).
You also need anti-abuse to stop bitcoin miners from using your system. GitHub probably have full-time employees working on it.
> Like bitcoin mining, there could be some competition between 3 parallel builds to pick the winner if the output is the same.
It's a lot more complicated because many builds are not deterministic, you need to store artefacts, build secrets, etc.
Companies like golem.network or iex.ec have been working on this problem for a decade and they are still not easy to use.