Thanks to Kotlin's interop with Java, Kotlin programs could already work with Protocol Buffers by simply using the classes that the Protocol Buffers compiler is able to generate for the Java language.

Google released an FAQ detailing Protocol Buffers, along with source code for the Java, Python, and C++ protocol buffer compilers.

Why did Google decide to go Open Source? "We have many other projects we would like to release as [O]pen [S]ource that use protocol buffers, so to do this, we needed to release protocol buffers first.

Based on HTTP/2 for transport, and a technology called Protocol Buffers for defining the data format, gRPC is designed to be a cross-platform protocol with support for multiple languages.