K2 and Community Builder integration is now possible using a series of files available from JoomlaMagic. See
www.joomagic.com/downloads/extensions/cat_view/73-extensions
...
With these files your K2 user avatar will be displayed in K2 modules and items. The avatar will link back to the CB profile and if you use the CB Author Tab plugin, the links from articles in CB will route to K2 items. To see a working version of this please go to
www.theicpm.com
Please take notice: This is a set of "Hacked" files. These are not plugins. We strongly encourage you to back up the original files before you upload these files through your FTP. With this solution you can use CB login module and CB registration
Overwrite these files with the downloaded files
K2 Component
..\components\com_k2\helpers\route.php
..\components\com_k2\models\itemlist.php
..\components\com_k2\templates\default\item.php
K2 Module
..\modules\mod_k2_content\helper.php
CB Plugin
..\components\com_comprofiler\plugin\user\plug_cbmamboauthortab\cb.authortab
If you are starting with a fresh K2 install - follow these additional steps:
2) Install plg_user_k2. It will automatically insert users when user registered in CB and will assign to group
3) from Back-end , K2 dashboard click "Import Joomla! content " it will import all joomla articles.
and CB "my articles" tab will show only K2 articles.
NOTE REGARDING SUPPORT: We hired a Joomlancer to complete this work, so little support is offered. Use at your own risk.