In later versions of macOS it has been replaced by DiskImageMounter for mounting the images and Disk Utility for creating them.
[1][5] Versions of Disk Copy in Mac OS X added support for the newer Universal Disk Format (UDIF) image format, introduced with DMG files in Mac OS X.
Although the last official public release of Disk Copy for Mac OS 9 was version 6.3.3, there was to be a version 6.5 that supported OS X's UDIF image format.
As such the OS 9 version of 6.5 only ever made it to beta 13 before development on it stopped.
Disk Copy was also the name of an Apple utility distributed with some of the earliest versions of the classic Mac OS.