I don't know what 'free' means for the project, but open source and 'free as in freedom' are not redundant these days. While open source is legally indistinguishable from free software, time has proven that open source software can be designed in non-free ways. Examples:
- Bloating codebase so much that it can't be audited, extended or forked easily
- Tightly controlling the development
- Open shims for opaque blobs
- Hiding documentation and troubleshooting information
Free is a term used by the community for decades, literally in the name of the Free Software Foundation. I guess you could argue that their need to explain what free means indicates it was a bad choice to use, but it is pretty standard now.