To put the record straight copyright is an automatic right. Therefore when you produce a creative work you own the copyright in it There are a few exceptions so for example if you have a contract of employment, the contract will generally state that when you are employed the employer owns the copyright of material you produce at work
Copying or adapting someone else’s work is a ‘restricted act’. An adaptation is a ‘derived work’. If someone adapts your work, you still own it. There is no acceptable percentage of changes.
You have every right to object if they publish such a work when you have not given them your permission to do so. You are also entitled to reclaim any money they make from selling your work. They could seek your permission to use the work as the rights owner, however, you will be able to charge a fee and/or royalties for this.
Read more about copyright. If you would like more detailed information about copyright please ask for our Copyright White Paper.