Table of Contents
There are a few other packages implementing a SRS (spaced repetition system) based on org-mode.
Below, I've listed a the ones I've found so far that are actively maintained and implement a lot of useful functionality.
Thanks to the maintainers and all contributors for their work on these projects!
Other (Open Source) SRS
The Repetition Spacing Algorithm of org-fc is very similar to the one used in Anki.
When working with a large collection of mostly text-based items, it's important to have powerful editing possibilities.
org-fc is a SRS built into a (the) most powerful text editor.
Org-Mode
Among the other org-mode based SRS I've found so far, org-fc is unique in that each headline can have multiple "positions" that are reviewed independently from each other.
This is very useful for Cloze Deletions .