I am so confused about GPL and LGPL?

[xuezi]

Who can tell me what the difference between GPL and LGPL is? For example, PJA(Pure java AWT) is GPL and JFreeChat is LGPL, I know they are all free software. but I've heard that they can't work together because of license(I have ever seen such topic from this forum), why(Am I wrong)??
I am so appreciated for your help!

[jwenting]

GPL is extremely restrictive. If you use any GPL libraries in your work you have to release all of your work (including any libraries you use that were made by others) under GPL as well.
Therefore unless you want to use GPL as your own license (you won't if you're halfway sane) and use only other GPL libraries you can't use any GPL libraries at all.

LGPL is slightly better, allowing you to choose your own distribution license for your own code.

[david.gilbert]

GPL is extremely restrictive. If you use any GPL libraries in your work you have to release all of your work (including any libraries you use that were made by others) under GPL as well.

There are far more extreme licences when it comes to restrictions. For example, most proprietary software licences won't allow you to incorporate that code into your own work under ANY circumstances. The GPL at least gives you an option, if you are willing to reciprocate.

Therefore unless you want to use GPL as your own license (you won't if you're halfway sane) and use only other GPL libraries you can't use any GPL libraries at all.

So you are suggesting that only insane people develop and release software under the GPL? That's an interesting viewpoint, but not very rational.

LGPL is slightly better, allowing you to choose your own distribution license for your own code.

The LGPL is a nice compromise, and I believe it was/is a good choice for JFreeChart.

[david.gilbert]

Who can tell me what the difference between GPL and LGPL is? For example, PJA(Pure java AWT) is GPL and JFreeChat is LGPL, I know they are all free software. but I've heard that they can't work together because of license(I have ever seen such topic from this forum), why(Am I wrong)??
I am so appreciated for your help!

GPLed software can only be combined with other GPLed software (note that you can take any LGPLed library and apply the terms of the GPL to your copy, so it is no problem to include LGPL libraries into GPLed applications).

LGPLed software (like JFreeChart) can be incorporated into any application, free or non-free, provided that a few simple requirements are met:

(1) You include a notice that JFreeChart is free software under the terms of the LGPL;
(2) You include a copy of the LGPL when you distribute your application, so that your users know that JFreeChart is free software with no warranty;
(3) You make available the JFreeChart source code, including any changes you made to it;
(4) You make it possible to modify JFreeChart and run the modified version against your application (you must allow reverse engineering of your software for the purpose of debugging the new combination).

Anyway, if you are interested in more information about free/open source licences, the following provides a pretty good overview:

http://www.oreilly.com/catalog/opensour ... erens.html