CKEditor 4 is highly customisable and can be adjusted to your needs. It means that you can select only the features and languages you will be using instead of installing the full package.
If you want to use the CKEditor 4 source code in your test or production environment, never use the source version of CKEditor 4 on production. Instead, you must create a CKEditor 4 ‘build’ or ‘release version’, which is an optimised, production-ready CKEditor 4 distribution. Use the source version for plugins development only.