while it doesn't prevent rust from being used, it is still a hurdle which must be overcome. Building and maintaining a multi-language build system has significant costs, especially with a project with as much history and wide use as ghostscript.

It is so easy and well documented that first page of google results for “rust autotools” does not contain anything about how to integrate rust code into existing autotools project.

Another issue is general subtle brokenness of rust tooling on anything that is not linux on amd64.