The document outlines several arguments for being open with educational materials:
1) The technical argument is that there is no education without open source materials.
2) Politically, being open can increase exposure for educational institutions and individuals like teachers and researchers.
3) Economically, research shows open materials may increase sales of related books and resources through greater exposure.
That's a concise three sentence summary of the key points made in the document about arguments for being open with educational materials.