许可 – JDK源代码许可不一致

我安装了最新的JDK(1.7.0_21).当我在Eclipse中查看基础类的源代码时,例如java.lang.String,文件顶部的许可证为：

/*
 * Copyright (c) 1994,2010,Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

此源代码来自JDK版本附带的src.zip文件.

当我在这里查看源代码时：
http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/7-b147/java/lang/String.java?av=f

…我看到了GPL v2.0许可证标题.

/*
 * Copyright (c) 1994,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.
 *
 * This code is distributed in the hope that it will be useful,but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not,write to the Free Software Foundation,* Inc.,51 Franklin St,Fifth Floor,Boston,MA 02110-1301 USA.
 *
 * Please contact Oracle,500 Oracle Parkway,Redwood Shores,CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

据我所知,JDK 1.7作为完全开源发布,在GPL 2.0下获得许可.

有人可以解释许可证差异吗？