Final answer:
Francis should use a Creative Commons Attribution 4.0 International (CC BY) license for his picture book, allowing free usage while preserving his copyright and requiring attribution.
Step-by-step explanation:
Francis can utilize a Creative Commons Attribution 4.0 International (CC BY) license for his picture book. This license allows teachers and readers to freely download, use, and distribute his work, accommodates the manuscript being openly licensed, and fosters the 5Rs of openness: revise, remix, redistribute, reuse, and retain. However, it also requires them to provide attribution to Francis as the original author, thus maintaining his copyright.
Moreover, the CC BY license supports Francis's desire for his book to be adapted and expanded upon, as it enables creation of derivative works, whether for educational purposes or research. This aligns with the ability to remix content as needed for various learning environments while ensuring his work remains protected under copyright laws. Finally, such a license also provides the flexibility for creation of custom versions, contributing to the ubiquity and adaptability of his educational content.