The majority of free ebooks are public domain works, which anyone can download or share. You can get these from places like mobileread.com, gutenberg.org, feedbooks.com, manybooks.net, and also from the major book vendors. In the US, public domain is mostly (but not all) stuff published before 1923). Different countries have different public domain rules. Canada and Australia have more access than the US (shorter copyright times for older stuff).
Publishers occasionally offer fairly current free books for a limited time. I've found some that were great, and by major authors, but the majority are stuff from independent publishers, and stuff that I would not be interested in (e.g. self-help stuff, cookbooks, romances, etc.). Mostly, the major publishers give away things like the first book in the series, so you have to buy the other books to read more about that character. Pretty much to be expected - a promotional thing.
Baen Books (webscription.net) has some free books, and the fifth imperium (
http://baencd.thefifthimperium.com/) gives away the content of the Baen Books CDs that come with hardcovers (this is legit, and ok with Baen). Of course, this is science fiction and fantasy, and may not suit your friend.
If books are public domain, you may share them, but most other sites preclude you from doing that (you agree to that when you use their site to download, e.g. Amazon). But, if the book is offered for free, anyone can download it to their own account. No need to share.