EasySync has been discontinued as a commercial product.
This page has a download for a freeware version compiled for later versions of MacOS than the paid version supported.
Note that this version (V1.2+) is supplied without warranty or support.
NOTE: If you receive a "The application can't be opened" error message, then please use a third-party unzip application, for example https://www.keka.io/. Apple's default Archive utility does not always keep permissions on download of apps.