CKEditor, the third-party rich text editor used in vBulletin 5, is disabled for all mobile devices including some tablets like iPad. This is because CKEditor does not have full mobile support yet. But according to CKEditor documentation on mobile support at http://docs.ckeditor.com/#!/guide/dev_browsers-section-a-word-about-mobile-environments, CKEditor is generally compatible with iOS6+ (iPhone and iPad) and Android. This modification enables the CKEditor for those devices on your vBulletin 5 forum. Full mobile support will be introduced in CKEditor 5. vBulletin 5 uses CKEditor 4.3.3 (vBulletin 5.1.2 and above). Latest version of CKEditor as of this writing is 4.4.2. vBulletin CKEditor is five releases below the latest CKEditor version. So you can imagine when CKEditor reaches version 5 with full mobile support, it would take years from that point for vBulletin to updgrade their editor to this version. So you will need this modification for a long long time.