We will provide our own desktop clients based on https://github.com/owncloud/client as well as the Android client based on https://github.com/owncloud/android.
With the iOS app it’s a little bit more tricky because due to it’s license we’re not able to distribute https://github.com/owncloud/ios. We’re working on a solution for that as well and might be able to share some news on that front soon 