Though Macs Fan Control is not open-source, we use this GitHub repository to track bugs, feature requests and technical support problems (see issues).
The repository also contains Macs Fan Control translations as .xml files. Fork the repository, update existing translation (or create a new one) and simply create a pull request. Always leave %1 (%s), %2, etc in the string, it's a replacement pattern required by the program.
Release archive contains the list of binaries for every version of the app with release notes.