In case the developer didn't decide to go opensource or not. Thanks.
crates.io only distributes source code. If you want to distribute crates in binary form, you will need to publish them some other way.
The lack of a stable ABI makes it difficult to distribute Rust libraries in binary form for general use. The most reliable workaround is to expose a C ABI to your Rust library, but this puts a lot of constraints on the library's interface. One alternative might be to provide access to source packages under NDA. Another would be to distribute pre-compiled rlibs for every toolchain/platform combination that your customers need.