This week's book giveaway is in the OCAJP forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide 1Z0-808 and have Jeanne Boyarsky & Scott Selikoff on-line! See this thread for details.
On the other hand EJB3 is backward compatible. What this means is, you can have EJB2.x style beans in your EJB3 application. The "Remote interface" is specifically meant for these EJB2.x beans. So a "Remote Interface" (implies this is for a EJB2.x bean) will be extending from the javax.ejb.EJBObject.