Web UI integration

How can I embed a web ui in my web client to pick or upload files to ownCloud?
e.g. Google Drive Integration on Trello, http://blog.trello.com/introducing-google-drive-integration

Files can be uploaded to ownCloud via WebDAV like shown in e.g.:

Thanks, but both links are error for me.

Click on the linked thread and use the links from there. The embedded post just broke the URLs.