[VPM] GNU GPL vs. GNU LGPL

[Darren Duncan]

At 7:10 PM -0800 12/28/06, Jer A wrote:
>what is the main difference between GPL and LGPL (in easy english) ?
>what are the advantages and disadvantages, including loopholes etc.
>-thanks in advance, for those who care to answer.

The GPL and LGPL are essentially the same except that the LGPL grants 
an extra permission which the GPL doesn't.  The GPL requires that if 
you distribute a GPL covered work along with your own work that 
depends on it, then the whole combination, including your work, has 
to be GPL-licensed.  The LGPL says you don't have to make the 
combination GPL, and your own work has whatever license you want, 
though the LGPL covered work remains LGPL.

With version 2 of each of those, both licenses are self-contained 
with all their text.  With version 3 of each, the LGPL is explicitly 
just a GPL plus permissions, and you distribute copies of both 
licenses if you use LGPL.  Version 3 hasn't been officially released 
yet, but should be no later than March of 2007.

If you release your code LGPL, then others that make add-ons to it 
can release their code closed-source if they want, where if yours is 
GPL, then their add-ons have to have their code available too, if 
they distribute yours together.

Personally, my approach is to use GPL for any of my important or 
truly significant stuff (such as my QDRDBMS program), with my own 
linking exception granted for free software (eg, Apache, Mozilla, 
public domain, ...) to keep their own licenses, but this doesn't 
extend to closed-source extensions ... those people can pay me for a 
proprietary license like with MySQL AB.

I use LGPL for trivially simple things like my Locale::KeyedText library.

I will be expressly using version 3 of both licenses when said 
licenses are done, most likely; meanwhile I am using "version 2 or 
later" with both.

-- Darren Duncan