For what it's worth, speaking in terms of free software rather than open source (since the author of the featured article might be receptive to the moral ideals

For what it's worth, speaking in terms of free software rather than open source (since the author of the featured article might be receptive to the moral ideals of free software rather than merely the business-pragmatic ideals of open source): if the vendor lets you download the source code of free software already in your possession without an excessive burden (one valid option being letting you download a zip/tar.gz of the entire necessary codebase; one invalid option being forcing you to copy files one at a time) then the software is free software regardless of whether the vendor accepts any third-party contributions.