As of March 7, 2015, ownCloud 8 does not ship with the Tasks app. The developer is working to make it ship with ownCloud 8 by default, but in the mean time, you can easily enable it yourself. Just follow the instructions from the github Tasks page:
- Enable the ownCloud Calendar app. It will be located under Recommended or Not Enabled.
- Run the following code on your computer with ownCloud
git clone https://github.com/owncloud/tasks/
- Enable the ownCloud Task app:
Enjoy your tasks!