2

The LGPL point 3 says:

3. You may opt to apply the terms of the ordinary GNU General Public License instead of this License to a given copy of the Library. To do this, you must alter all the notices that refer to this License, so that they refer to the ordinary GNU General Public License, version 2, instead of to this License. (If a newer version than version 2 of the ordinary GNU General Public License has appeared, then you can specify that version instead if you wish.) Do not make any other change in these notices.

Once this change is made in a given copy, it is irreversible for that copy, so the ordinary GNU General Public License applies to all subsequent copies and derivative works made from that copy.

This option is useful when you wish to copy part of the code of the Library into a program that is not a library.

Can anyone explain what does it mean?

Can one take a LGPL library and use it as GPLv2?

3

Can one take a LGPL library and use it as GPLv2 ?

Yes, use it, modify it and redistribute it as GPL v2 (or later). This is a form of explicit extended LGPL -> GPL compatibility.

  • I find it odd, it looks like some sort of non explicit double licensing. – ossx Sep 5 '17 at 11:40
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    That's not double licensing that's a relicensing permission. Technically, this is not the same, although the effect is pretty much equivalent. – Zimm i48 Sep 5 '17 at 11:40
  • But isn't this a way of avoiding the license conditions of the LGPL ? – ossx Sep 5 '17 at 11:41
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    Yes, of course but the goal of the LGPL authors (which are the same as the GPL authors) is not to make the life of people writing GPL software more difficult. So this is a special permission for them. To understand LGPL philosophy, you need to be aware that this is not the king license of the GNU family. – Zimm i48 Sep 5 '17 at 11:43
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    One furthermore should understand that all rights granted by the GPL are also granted by the LGPL, but not vice versa. Converting a copy of an LGPL-licensed work to GPL therefore constitutes an (explicitly allowed) narrowing of the licensing terms. And yes, the permission to do so serves the FSF's express interest in promoting the GPL over the LGPL. – John Bollinger Sep 6 '17 at 13:57

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