If you contribute changes to the existing flash cards they'll be licensed under "Creative Commons BY SA" (most likely), every flash card will tell you the licen

If you contribute changes to the existing flash cards they'll be licensed under "Creative Commons BY SA" (most likely), every flash card will tell you the license if you open "view" it. If you create your own they'll just belong to SYL, though, single flash cards are not copyright-able so there is no issue if you steal those flash cards. And I personally would have no issues when people re-use content for other use.