However, in late 2005 / early 2006, when we spun it out[1] as a standalone corporation and registered the domain name, etc., I did request, and receive, explicit permission from the authors/maintainers of rsync to adopt, and use, the rsync.net name.
[1] rsync.net began operation in 2001 as an add-on feature to JohnCompanies which was the first provider of the VPS as we now know it.