McCaffrey was notorious for her restrictions on fanfiction, role-play, and other fandom activities, but she has officially lifted said restrictions. This is widely viewed as a good thing by fans, but it has also resulted in a surge of badfic, particularly noticeable in the Pern universe. This is definitely a bad thing.
Her son, Todd McCaffrey, has also written books in the Pern universe. Opinions of their worth and status as canon vary.