Charles Bergeron of Albany College of Pharmacy and Health Sciences has launched an open source differential equations textbook project called Differential Equations. In the spirit of open source, Charles started with Jiri Lebl's "Notes on Diffy Qs" and is adapting it to his own purposes (strengthening the linear algebra portion of Lebl's text). Like many of us, Charles is a long-time user of open educational resources including: David Guichard's Calculus, its derivative Mooculus, Stitz and Zeager's Precalculus, and Maxima to provide visualizations
Charles says, "What perhaps makes my project different from others is that I mashed up content from several sources. The review section on factoring polynomials over the complex numbers comes from 'Precalculus'. The review of hyperbolic functions comes from 'Community Calculus'. I borrowed a few examples and applications (such as radioactivity and glucose absorption which are interesting to health scientists) from 'Elementary Differential Equations' by William F. Trench. And most of the content in the linear algebra chapter is from 'Linear Algebra' by Jim Hefferon. My outreach to those authors has been generally welcomed."
He has chosen the Creative Commons BY-NC-SA license for this work. In particular, he has added NC (non-commercial) clause primarily because the work is derived from works with the NC clause. If you use his book, let him know. If you want to contribute. Reach out to him.
Finally, his college library is planning 'launch party' for the book to coincide with Open-Access Week in October. He seeks creative ideas from the community on what that could be. Please put your ideas in the comments section.