在C++SGI-STL3.3时看到了一个词copyright
/*
* Copyright (c) 1996-1997
* Silicon Graphics Computer Systems, Inc.
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Silicon Graphics makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*/
这个涉及到一个软件开源协议：GPL协议，即generic public foundation，即GNU通用许可证，他使用的是copyleft，即copyright的反义词。
Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
GNU即GNU is not Unix，发音和革奴类似，Linux里面很多软件都是靠GNU实现的，比如GCC，EGCS，Emacs，GNOME等等。
开源yyds