Buf seems really nice, but I'm not completely sure what's free and what's not with the Buf platform, so I'm hesitant to make it a dependency for my little open source side project ideas. I should read the docs a bit more.
Buf CLI itself is licensed under a permissive Apache 2.0 License [0]. Since Buf is a compiler, its output cannot be copyrighted (similar to proprietary or GPL licensed compilers). DISCLAIMER: I am not a lawyer.
Buf distinguishes a few types of plugins: the most important being local and remote.
Local plugins are executables installed on your own machine, and Buf places no restrictions on use of those.
Remote plugins are hosted on BSR (Buf Schema Registry) servers [1], which are rate limited. All remote plugins are also available as local plugins if you install them.
It's worth to mention that the only time I've personally hit the rate limits of remote plugins is when I misconfigured makefile dependencies to run buf on every change of my code, instead of every change of proto definitions. So, for most development purposes, even remote plugins should be fine.
Additionally, BSR also offers hosting of user proto schemas and plugins, and this is where pricing comes in [2].
