...Stable tags are created from edk2/master based on validation with various platforms. Stable tags names use the format edk2-stable<4 digit year><2 digit month> and occur roughly every three months (starting from August 2018). UEFI Development Kit (UDK) releases pre-date the introduction of the stable tag, occur less frequently, and have a longer validation cycle. These are based on validation using various platforms. The year tag indicates the year of major specifications used for the release. The majority of the content in the EDK II open source project uses a BSD-2-Clause Plus Patent License.