PrimeNG LTS is as an annual subscription based service to provide a license for the finest compatible version suited to you. LTS covers the prior two versions from the latest release, this means up to 18 months of almost weekly releases to bring the latest defect fixes and security updates to your project. As an example, since PrimeNG moved to Angular 11, PrimeNG 9 and 10 is now on LTS support whereas STS (short term support) versions of PrimeNG 11 will be open source under MIT license for at least 6 months until PrimeNG 12 is released. Here is a timeline to visualize the LTS support.
If you are not planning to migrate to Angular 11 and PrimeNG 11 yet, we strongly suggest LTS versions to receive weekly performance, security and quality enhancements as PrimeNG 9.x and 10.x are in active development.
Please visit the official announcement for changelog and more information;