Nearly three years after the release of CUPS 2.2, CUPS 2.3 came out and was delayed by more than one year.
CUPS 2.3 is an important update due to licensing changes. Apple has decided to re-license the print server under the Apache 2.0 license. But due to various linux specific utilities that are GPLv2 and non-Apple, this poses a problem. Therefore, Apple decided to add an exception to their Apache 2.0 license to allow software to be associated with GPLv2 software.
CUPS 2.3 also includes security fixes, many bug fixes, support for IPP printer presets, a new "ippeveprinter" utility, and various other improvements.
Source: linux.org.ru