Chris McCormick chris at mccormick.cx
Wed Mar 28 08:25:06 CEST 2007

On Tue, Mar 27, 2007 at 08:37:46PM -0400, Chuckk Hubbard wrote:
> Was PD previously under GPL?


> So after software has been released under a license, it is possible to
> retroactively change the license?  Sounds strange to me.

If you are the copyright holder, you can do whatever you want. In some
cases it's very difficult to change the license. For example if there
are many copyright holders, like the Linux kernel, you must get them
all to agree. Although recently Bruce Perens posted an interesting
article saying that this wasn't entirely true - Linus could state that
he wished to change the license, and then just change the minds of those
who disagreed with the move. He would not have to get every developer,
including the dead ones, to state their agreement - silence would be
taken as assent.

One interesting and not-very-often-mentioned repercussion of this is that
you can dual license your own software. For example, I can license my
library GPL so that any changes to it must also be GPL, but I can also
sell the exact same library to a company under a different, proprietary
license if that company doesn't want to adhere to the GPL. That is
completely legal, and I think it was what Trolltech did with Qt.

Note that if you retroactively changed your GPL licensed software to
be non-GPL licensed, people could still fork the code at the last point
that it was licensed GPL and continue developing as before.



chris at mccormick.cx

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