This doesn't seem like hindering anything. There's no legal block, there's no stopping you from RTFM and following the steps, it's not as if the author is even hiding the steps.
Paying for convenience isn't
a hinderance.
You just want the convenience at zero price.
Shameless plug: We just started supporting rustc compiler caching and released it as part of our support for open source projects: https://crave.io/#opensource
We're showcasing the Libra project to start with and would be up for adding other projects that the community is interested in.