Terminology description:

• Subscription Advantage (SA) Date: A date present in perpetual license files, introduced to limit upgrades to NetScaler versions released only up to a certain date.
• Burn-In Date (BID): A date associated with every NetScaler version and build.

The following changes are introduced in Perpetual licensing:

Change 1: SA Date check and enforcement:

This check and enforcement is introduced to block NetScaler customers who are running NetScaler instances on perpetual licenses with expired maintenance, resulting in unsupported deployments.

If the Burn-In Date of the NetScaler build to which you are trying to upgrade to is later than the SA date in the perpetual license file used on your NetScaler instance, your NetScaler instance becomes unlicensed after the upgrade. Some NetScaler VPX™ versions already had this check and enforcement. It is now introduced for NetScaler form-factors: VPX, MPX, and SDX, starting from the following NetScaler releases:

• NetScaler ADC: 14.1 51.x, 13.1-60.x, 13.1-37.x (FIPS)
• NetScaler SVM: 14.1 51.x, 13.1-60.x

To find the SA date of the perpetual license used on your NetScaler instance, see your perpetual license file for the SA date in YYYY.MMDD format as shown in the following sample image.

This check occurs during boot up after a NetScaler upgrade. To avoid your NetScaler instance becoming unlicensed, obtain a supported NetScaler license with active maintenance.

Change 2: Burn-In Date specific to each build:

Earlier, the Burn-In Date for all builds across a major NetScaler version used to be the same. For example, all builds under NetScaler version 13.1 used to have the same Burn-In Date. Now, each unique NetScaler build has its own Burn-In Date (approximately based on its release date), starting from the following NetScaler releases:

• NetScaler ADC: 14.1 51.x, 13.1-60.x, 13.1-37.x (FIPS)
• NetScaler SVM: 14.1 51.x, 13.1-60.x

SA Date check and enforcement, and Burn-In Date specific to each build have been introduced starting from the following NetScaler releases:

• NetScaler ADC: 14.1 51.x, 13.1-60.x, 13.1-37.x (FIPS)
• NetScaler SVM: 14.1 51.x, 13.1-60.x

If you are using a perpetual license on your NetScaler instance and have active maintenance, but have not replaced the old perpetual license file with the license file provided with your latest maintenance renewal (that is, you did not use the latest license file with updated SA date and are still using the older license file with old SA date), your NetScaler becomes unlicensed if you upgrade to NetScaler builds that have the SA date check and enforcement. To avoid this impact, use the latest file that you received during your most recent maintenance renewal.

After upgrading a NetScaler to 14.1 51.x, 13.1-60.x, 13.1-37.x (FIPS) or newer builds when using file-based licensing, the NetScaler could go into FREEMIUM license mode. This is due to the firmware Burn-in date being newer than the SA date present in the license file. The license file used by the NetScaler must be updated with the newest available file from the License Portal, which would have the newest SA date.

Documentation:

https://docs.netscaler.com/en-us/citrix-adc/13-1/licensing.html#changes-related-to-perpetual-licensing

https://docs.netscaler.com/en-us/citrix-adc/current-release/licensing.html#changes-related-to-perpetual-licensing

Release documents for CTXENG-68283: Perpetual Licensing changes - SA Date enforcement and NetScaler build-specific Burn-In Date 

https://docs.netscaler.com/en-us/updates?product=NetScaler%2520ADC%2520%28includes%2520NetScaler%2520Gateway%29&version=14.1&build=51.80

https://docs.netscaler.com/en-us/updates?product=NetScaler%2520ADC%2520%28includes%2520NetScaler%2520Gateway%29&version=13.1&build=60.32