Technically correct because by the definition that Wikipedia gives (http://en.wikipedia.org/wiki/Public_domain), non-enforcement of a trademark could lead to forfeit of the rights on that trademark, and that is one of the options mentioned in the definition.

But not idiomatic because the term is much more commonly used in copyright, rather than trademark, where it has a very specific legal meaning. A copyrighted work enters the public domain when the copyright expires (or in old cases, if the owner failed to renew the copyright).

That is, "generic usage" refers to things like people using "a kleenex" to refer to any facial tissue or "a xerox" to refer to any mimeograph. However, when people say "JavaScript", they always mean the exact same JavaScript: the one Oracle owns.

(It could be argued that they mean ECMAscript—but that's a bit like saying that people who say "pass me a coke" when what they have available are cans of no-name generic cola (with trade-dress explicitly reminiscent of Coca-Cola's, no less) are actually thinking they want any generic cola, rather than that they want a Coca-Cola and that the can you have to offer is merely an adequate stand-in.