HumHub

HumHub is built on top of yii2 php framework. It uses two versions, free and paid. Paid version is called Enterprise and has additional theme and functionalities. Both free and paid versions are agpl, that mean that you can use it but you have to shere your code with community. If you want to keep your code you can buy commercial licence. Humhub organise users using profiles and spaces which are simular to facebook groups. User can follow other user or space, he can join space to get rights to post content inside spaces. Modules available are: wikis, tasks, etherpad notes, pools, meetings, files...