When you open Messages for the first time, you’re invited to sign in to (or sign up for) your iCloud or Apple account. Take the opportunity to set this up; you’ll be glad you did.
But as Figure 18-1 shows, you can always sign up for a different kind of account, either now or later.
Figure 18-1. Top: The first time you open Messages, you’re supposed to enter your Apple ID (your iCloud, .mac, or .me address) and password. That way, you can join in the thrill of iMessaging. If you click Not Now (and then click Skip in the “Are you sure?” box), then you’re offered the chance to sign in to a different chat service (middle). Bottom: Of course, you can always add one of these accounts later. In System Preferences, click Internet Accounts, described on page 322—or, in Messages, choose Messages→Preferences, click the Accounts button, and click the button.
Among your options:
Jabber is a chat network whose key virtue is its open-source origins. In other words, it wasn’t masterminded by some corporate media behemoth; it’s an all-volunteer effort, joined by programmers all over the world. There’s no one Jabber chat program (like Yahoo Messenger). There are dozens, available for OS X, Windows, Linux, Unix, iPhone, and so on. They can all chat with one another across the Internet ...