I have some legal questions regarding [OpenJDKs source header](http://hg.openjdk.java.net/jdk7/jdk7/jdk/file/00cd9dc3c2b5/src/share/classes/java/util/ArrayList.java):

```
/*
 * Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
(...)

```

* Is it GPL-conform to define a comment-part of a source-file (in this case the header) as "must not be modified"?
* Do other GPL-licensed open-source projects derived from this sources need to obey this "statement"?
* Does Oracle really have a Copyright on these GPL-sources?
* Is it GPL-conform to state that it's ***only*** allowed to `modify [the software] under the terms of the GNU General Public License version 2`?
* What does this mean for GPLv3 open-source projects which are using these (possibly modified) sources?
* Do I have to fear editing (and publishing) this file (and maybe adding something to the file header) in my own GPLv3 open-source project?