Dual license review

[Russell Nelson]

Iain Barker writes:
 > This is hopefully a simple question (!)

Simpler than you thought.

 > We have some in-house written software which is currently under
 > a proprietary license, and we would like to release it into the
 > free software community under GPL.

No problem.  License it to the free software community under the GPL.
Continue to use it and sublicense it to your customers under the
agreement you're using now.  You're the copyright holder.  You get to
do this.

You are well advised, though, to get a permissive license or copyright
assignment from anybody contributing to the GPL'ed project.  You're
also well advised to tell both the GPL users and the proprietary users
of the other license.  First, so that the proprietary users aren't
surprised by open source projects using the same code.  Second, so
that GPL users realize that they can purchase  a proprietary version
which lets them escape the GPL.

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