Yes.
All the books, lessons, and other documents on this website are PDF files, which you can download to your computer for free.
A few of the SignWriting books are also available as bound hardcopy books. In these cases the website provides a link to the Amazon website, where you can purchase the hardcopy version of the book.
The SignWriting textbooks and lessons are licensed under the Creative Commons ShareAlike License. This license lets you use, modify, or redistribute the SignWriting textbooks or lessons, for free.
However, if you modify or redistribute these documents, you must give appropriate credit, provide a link to the original license, and indicate if you made any changes.
The license has other rules, but these are the main ones.
Creative Commons ShareAlike License