In the sense you need here, e-publisher names the business of producing books, magazines, or newspapers that are designed to be read on a computer, a phone, or an e-reader — not printed on paper, or not only printed. The trade makes files people can open as e-books or on a website, then sells or gives them out. Though actually, in real talk e-publisher very often points to the company or the person who does that work; the trade itself is also called e-publishing. Same e- as in e-book. It is a business word, a little official, used in the industry more than at the dinner table.

電子出版商（詞典這義也指這門生意本身，也就是電子出版；口語卻常指那家公司）