Hi there! You can definitely make your book or magazine with Blurb and keep it private. When you upload a book to your Blurb account, by default it is private and only you can see it and buy it. We offer you the tools to publish and sell your book, but you don't have to sell it if you don't want to.
Also, the copyright for your content remains yours. We are offering the authoring tools and the printing/binding of your masterpiece. The content, book, and all rights are yours. This is detailed in section 8 of our terms and conditions: http://www.blurb.com/terms. Section 6 of our End User License Agreement also clarifies that you retain all title/rights to your content as used in our books: http://www.blurb.com/software-eula
I hope I've answered your questions but feel free to contact our Customer Support team if you want to know more: https://support.blurb.com/hc/en-us/requests/new

Best,
Blurb Team

I made photo albums for elderly parents and friends who have passed away. Gave as gifts but now want a copy for my family. Held hostage by Blurb who I had used to lay out and design books in the first place.