OpenIntro features a number of free books that can be used in high school and AP statistics courses. The license on these datasets is currently unknown. You can find out more about OpenIntro at https://www.openintro.org.
Picostat is a web-based opensource statistical application framework based on Drupal 8 and ℝ. Drupal can be used to manage user datasets and perform basic statistical analysis with a NoCode end-user interface ideal for non-technical users. Custom applications can be easily integrated into the system using webforms and ℝ language syntax.