I'm surprised by some posters here that show no respect at all for Opera... like it or not, it's probably the most innovative browser arround.
They were the first with tabbed browsing (could you imagine living without it now?), were the first with a pop up blocker, mouse gestures and tons of other stuff.
Look for more info here: http://www.opera.com/portal/15/years/
They might have slowed down with Opera 15, and I didn't like the change from Presto either, but I'm using Opera 15 and I'm enjoying it more than Opera 12 (though I miss a lot of features, but surfing Facebook isn't a hell anymore).
They do know that a lot of features aren't available yet. They will add new features again, but give them some time.
And more on topic, Opera has every right to sue this person if he really did steal something, but this isn't our concern. If Opera feels that something was stolen, and they feel that it is enough to sue, Try to google opera sues and you will see that it's basicly the only time that opera sued anyone themselves, or one of the few times. Look up google sues or microsoft sues, you'll see something completely different...
We don't even know what was stolen, and as long as we don't know that we shouldn't argue. It could be something very obvious, but alas we do not know yet.