You can download Dragondisk at http://www.s3-client.com/
The provider you should choose is: Other S3 compatible service
Service Endpoint is: nl.dadup.eu
AccessKey & Secret key can be found in https://admin.tuxis.nl
Make sure that, in the account settings in Dragondisk at the advance tab,
the "'Expect: 100-Continue' HTTP header" is NOT selected.
After configuring the account you can connect to your daDup storage from the pulldown menu.
And you are now able to create a bucket.
For more information follow the quick start guide on their website.
But first: Create a daDup account
(if you don't have one).