According to the Wikipedia JavaScript article the name "JavaScript" was the result of a co-marketing deal between Netscape and Sun. (It was originally called "Mocha" and then "LiveScript".)
In other words, this was a very deliberate step on the part of Sun, not a case of Netscape trying to stomp over their name.
From the linked article:
"JavaScript" is a trademark of Sun
Microsystems. It was used under
license for technology invented and
implemented by Netscape Communications
and current entities such as the
Mozilla Foundation.
and further:
Due to the widespread success of
JavaScript as a client-side scripting
language for web pages, Microsoft
developed a compatible dialect of the
language, naming it JScript to avoid
trademark issues.
So, there was no need for Sun to sue as the name was either licensed (Netscape/mozilla) or technically not used at all (Microsoft)