Final answer:
The creator of a work typically holds the copyright when contracts do not specify otherwise. Under U.S. law, copyright is designed to protect original works of authorship and lasts for the creator's life plus 70 years. Exceptions occur in cases like work made for hire or when using openly licensed material with proper attribution.
Step-by-step explanation:
When contracts do not explicitly address copyright ownership of drawings or other creative works, the default rule under U.S. law is that the creator of the work holds the copyright. According to the U.S. Copyright Office, copyright is a form of protection for original works of authorship, which includes various forms of artistic expression, and typically lasts for the life of the author plus 70 years. If there is no contract specifying otherwise, the individual or entity that created the drawings would own the copyright.
However, this general rule has exceptions, such as when the work is created as a work made for hire, in which case the employer or commissioning party would be considered the copyright owner. Since the terms of the contracts are essential in determining the ownership of copyright, it is crucial to consult the specific agreements or legal counsel when in doubt. If you are dealing with art from textbooks or similar resources and the copyright is not clearly attributed, OpenStax guidelines suggest that the art is probably openly licensed for use with appropriate attribution, as they provide with their openly licensed material.