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 10, PrimeNG 8 and 9 is now on LTS support whereas STS (short term support) versions of PrimeNG 10 will be open source under MIT license for at least 6 months until PrimeNG 11 is released. Here is a timeline to visualize the LTS support.
If you are not planning to migrate to Angular 10 and PrimeNG 10 yet, we strongly suggest LTS versions to receive weekly performance, security and quality enhancements as PrimeNG 8.x and 9.x are in active development.
Please visit the official announcement for changelog and more information;