Good and bad licence changes

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Changing from a copyleft licence (e.g. GPL) to a weak copyleft (e.g. LGPL) or to a permissive licence (e.g. Apache License) is almost never a good idea.

The rare situations where it's a good idea

Using a weak copyleft or a permissive licence can be a good idea if:

1. the functionality of the software is already widely available in proprietary software; AND
2. wide adoption will help break a form of control that proprietary software companies have on a domain (i.e. via a format or protocol); AND
3. the copyleft provisions are reducing adoption

Examples

Ogg Vorbis and Theora

The Ogg media suite is an example of when it's good to use a permissive licence.

VLC

A seemingly bad change:

• Left wondering why VLC relicensed some code to LGPL, Bradley M. Kuhn

QT toolkit

Bradley Kuhn says QT's GPL -> LGPL switch was a good move: LGPL'ing of Qt Will Encourage More Software Freedom

status.net and pump.io

status.net was AGPL, but the developers next genetion replacement was Apache Licence. The lead developer, Evan Prodromou says the change is because the software fits the three criteria mentioned above.

External links

• Why you shouldn't use the Lesser GPL for your next library, GNU Philosophy