Barnesandnoble.com Inc., the No. 2 online bookseller, said it started a program that lets users earn a commission on sales if they direct other people to the retailer's Internet site through links in their e-mails. Through the service, called MybnLink, members can earn 5% of sales generated through e-mail referrals or give the money to certain charities. Commissions are earned on sales of books, music, videos, software or magazines. A member could e-mail a friend recommending a book, for instance, and get the commission if the person uses the e-mail link to make a purchase. MybnLink, which started Monday, is the latest move by Barnesandnoble.com to compete with No. 1 online seller Amazon.com Inc., which got a two-year lead selling books online. Barnesandnoble.com said the program is the first of its kind and will increase its customer base and lower marketing costs. Barnesandnoble.com is jointly owned by Barnes & Noble Inc. and German media company Bertelsmann. Barnesandnoble.com said it plans to market MybnLink through Barnes & Noble stores, online advertising and other channels.