SWC is not a "TypeScript type-checker project", it's a bundler and compiler.
The type checker in the title refers to the author's work porting the TypeScript compiler tsc to Go, which is a different/additional project.
> Vercel is sponsoring and funding the work to port tsc to Go. We’re planning to open-source this work in the future. I’ll also be creating a bridge to use this new version of tsc with SWC.
From the author's blog post "I'm porting tsc to Go" - https://kdy1.dev/posts/2022/1/tsc-go
The author has gone back and forth on whether the work will be open-sourced.
> It will be developed as a propriety software.
Mar 2021 - https://github.com/swc-project/swc/issues/571#issuecomment-8...
> I'm considering withdrawing the plan for open-sourcing it.
Apr 2022 - https://github.com/swc-project/swc/issues/571#issuecomment-1...