That comment was written in 2007 when the original suggestion would have been somewhat more acceptable. In 2019, please do not use plaintext FTP for anything at all if you can help it, especially for a setup involving personal documents or other data you care about keeping private. Every single syncing solution worth anything today, open or proprietary – including Dropbox, Google Drive, iCloud Drive, Microsoft OneDrive, Syncthing, et al. – uses TLS or another strong form of transport encryption, and that should also be the absolute minimum bar for anything self-hosted, too.
There are many other better ways of building a Dropbox-like system on Linux these days than that advice, including the aforementioned Syncthing[1], but the appropriate update to that comment alone would be "getting a SSH account, mounting it locally with sshfs[2], and then using Git on the mounted filesystem".