License of gccgo frontend

[Ian Lance Taylor <iant at google dot com>]

I committed the gccgo frontend using a BSD-style license with this
boilerplate:

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

The frontend is currently tightly tied to gcc.  However, my goal is to
loosen those ties, and make it possible to use the frontend with other
compilers.  Therefore, it seemed to me that a BSD-style license was
appropriate, and since the runtime library already uses one, I used
the same one.

However, Joseph Myers pointed out that the gcc mission statement says
"Copyrights for the compilers are to be held by the FSF."  I think
when we wrote that line we were thinking of quite a different issue.
However, it is certainly true that having the gccgo frontend be
copyright "The Go Authors" violates that statement.

So I would like some guidance from the SC on what the right approach
is here.  This is my order of preference:

1) Keep the license as is (and add the AUTHORS file which I forgot to
commit, and which currently just says Google, Inc.).

2) Keep the BSD-style license but change the copyright of the gccgo
frontend to the FSF.  The runtime library, which is shared with the
other Go compiler, would remain under the existing license, as is
permitted by the mission statement.

3) Move the gccgo frontend to the GPL.

Obviously the complete gccgo program--the gccgo frontend plus the gcc
middle-end--will always be under the GPL, as it should be.

Ian