Part of Backdrop Core Since v1.2

The CKEditor module for Drupal is no longer needed for Backdrop CMS.

The ability to use a Rich-Text editor has been included in Backdrop since version 1.2.

Upgrade Instructions: 

There is no upgrade path for the CKeditor module yet. Please follow this issue for progress on the upgrade path. Until the upgrade path is complete...

If you are running the CKeditor module on a Drupal 7 site:

  1. Note the editor configurations you have applied to each editor, and which editor is applied to each text format.
  2. Disable and Uninstall the CKeditor module from Drupal 7.
  3. Upgrade your site to Backdrop CMS.
  4. Manually re-configure your text formats in Backdrop to match your notes form step 1.