Update free-programming-books-langs.md (#11777)

Added license notes to C and C++ books

books/free-programming-books-langs.md

@@ -441,8 +441,8 @@ Books on general-purpose programming that don't focus on a specific language are
 * [A Tutorial on Pointers and Arrays in C](https://web.archive.org/web/20180827131006/http://home.earthlink.net/~momotuk/pointers.pdf) - Ted Jensen (PDF) *(:card_file_box: archived)*
 * [Algorithms Design (in C)](https://www.ime.usp.br/~pf/algorithms/) - Paulo Feofiloff (HTML)
 * [Bare-metal programming for ARM](https://github.com/umanovskis/baremetal-arm) - Daniels Umanovskis [(PDF)](http://umanovskis.se/files/arm-baremetal-ebook.pdf)
-* [Beej's Guide to C Programming](http://beej.us/guide/bgc/) - Brian "Beej Jorgensen" Hall (HTML, PDF)
-* [Beej's Guide to the GNU Debugger (GDB)](http://beej.us/guide/bggdb/) - Brian "Beej Jorgensen" Hall (HTML)
+* [Beej's Guide to C Programming](http://beej.us/guide/bgc/) - Brian "Beej Jorgensen" Hall (HTML, PDF) (CC BY-NC-ND)
+* [Beej's Guide to the GNU Debugger (GDB)](http://beej.us/guide/bggdb/) - Brian "Beej Jorgensen" Hall (HTML) (CC BY-NC-ND)
 * [Build Your Own Lisp](http://www.buildyourownlisp.com) - Daniel Holden
 * [Build Your Own Redis with C/C++](https://build-your-own.org) - build-your-own.org (HTML) (:construction: *in process*)
 * [C Elements of Style](http://www.oualline.com/books.free/style/) - Steve Oualline
@@ -550,7 +550,7 @@ Books on general-purpose programming that don't focus on a specific language are
 * [Programming Fundamentals - A Modular Structured Approach using C++](https://archive.org/details/cnx-org-col10621/mode/1up) - Kenneth Leroy Busbee (PDF)
 * [Software Design Using C++](http://cis.stvincent.edu/html/tutorials/swd/) - Br. David Carlson, Br. Isidore Minerd
 * [Software optimization resources](http://www.agner.org/optimize/) - Agner Fog
-* [The Boost C++ libraries](http://theboostcpplibraries.com) - Boris Schäling (HTML)
+* [The Boost C++ libraries](http://theboostcpplibraries.com) - Boris Schäling (HTML) (CC BY-NC-ND)
 * [The Rook's Guide to C++](http://rooksguide.org/2013/11/26/version-1-0-is-out/) - Jeremy Hansen (PDF)
 * [The Ultimate Question of Programming, Refactoring, and Everything](https://www.gitbook.com/book/alexastva/the-ultimate-question-of-programming-refactoring-/details)
 * [Think C++: How To Think Like a Computer Scientist](https://greenteapress.com/wp/think-c/) - Allen B. Downey (PDF)