David Turner
© Free Software Foundation <>

Take the Free Software licensing quiz and test your knowledge of the GPL and LGPL.

As this Quiz represents the legal opinions of the FSF (but is not legal advice), only verbatim copying and redistribution is allowed. Translations must be approved by the FSF; please write to for details.

Joan writes a web browser and releases the source code under the GPL on her web site. Fred gives a CD with binaries of Joan's browser to his friend for her birthday. Which of the following does NOT satisfy Fred's obligation to make source code available:

Now Fred makes modifications to Joan's web browser, and distributes binaries on his web site. Which of the following fulfill Fred's obligation to distribute the source code of the modified browser?

Fred wishes to distribute Joan's browser linked to a third-party module. The third party module has the following license:

"This code may be freely modified, copied and distributed, so long as no fee is charged for it."

Would this violate the GPL?

Peter creates a library called LibIdo licensed under the Lesser General Public License. FooCorp distributes a modified version LibIdo library linked to their proprietary program Frobber. Which of the following is NOT an obligation of FooCorp?

Joan wants to distribute copies of her browser statically linked to Postfix (a mail server), which is released under the IBM Public License, a GPL-incompatible Free Software license. Other than Postfix, the browser includes only code on which Joan holds the copyright. Should she grant an exception to the GPL for this?

FooCorp sells binaries of Joan's GPL'd web browser on CD without source code. They include an offer to provide source code. Which of the following offers fulfills their obligations under the GPL?

Patty creates a library, and releases it under the GPL. Many people make improvements to this library, and submit them back to Patty, who incorporates them into newer versions of the library. Now Patty wants to make a proprietary version of this library. She makes two claims:

I. Because the original version was under the GPL, everyone who made improvements automatically assigned copyright on those improvements to Patty, so she doesn't need to ask permission before relicensing.

II. Because she is the copyright holder, she can relicense the code retroactively, so nobody can distribute old versions under the GPL anymore.

Are these claims true?

FooCorp distributes Frobber linked against an unmodified version of LibIdo. Does the LGPL require FooCorp to allow users to reverse engineer Frobber for their own use?

Now FooCorp modifies Joan's browser to include a technology they have patented. They distribute this modified browser on CD. Are there any requirements in the GPL on how they may license their applicable patent?

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