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I was reading over a products license information and found out that they use multiple iterations of the GPL license (GPL v2, LGPL, a few more). I was wondering if the product that is licensed violates the "four essential freedoms" of free software mean they are violating the GPL license.

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    I'm not sure how your first sentence leads to your second sentence. Are you simply asking, "If a license does not supply all four freedoms, does that necessarily imply that license is GPL-incompatible?" If so, how does your first sentence add to the question? (I don't mean to nitpick; I'm just concerned that I might not fully understand what you're asking.) – apsillers Dec 3 '17 at 0:21
  • No it's fine, I'm asking if an application follows the GPL v2 license, is it required to follow all four essential freedoms and if so is it a license violation if they blatantly break one of the four essential freedoms (ex apply a restriction that violates a freedom). – Bill Richard Dec 3 '17 at 3:33
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    Delete the first sentence to clarify this question. Maybe this is the wording you want: "If a GPL v2-licensed application applies a restriction which violates one of the four essential freedoms, is it a violation of the GPL v2?" It would help if you mention an example of a restriction, as some restrictions may be allowed by GPL v2 but not allowed by GPL v3. – Brandin Dec 8 '17 at 11:21
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The license text is legally relevant. The four freedoms form a philosophical fundament for these licenses, but are not part of these licenses.

The GPL licenses try to ensure these essential freedoms for all users. For example, the freedom to study the program is ensured because binary distribution of a software is only possible when the corresponding source code is also offered. It is not possible to deny these freedoms by adding restrictions to the GPL license.

E.g. the GPLv3 contains a mechanism to add extra permissions to the GPL. It therefore clarifies that except for a few cases like requiring notices to be kept intact, no restrictions may be added:

All other non-permissive additional terms are considered “further restrictions” within the meaning of section 10. If the Program […] contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term.

– GPLv3, section 7 “Additional Terms”

The GPLv2 contains no such language, but contains a “Liberty or Death” clause:

If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all.

– GPLv2, section 7
– also: GPLv3, section 12 “No Surrender of Other's Freedom”

That means: it is not possible to pick some terms from the GPL and leave others. If you publish software under the GPL, you must grant all rights that are part of the license.

The GPLv3 was created because there are some problems with the GPLv2, and that has to do with how the GPL ensures the essential freedoms:

  • Patents: The GPLv2 is a pure copyright license. However, the right to use and distribute the program may be restricted by patents. Therefore, the GPLv3 contains a patent grant. (This was also necessary to gain compatibility with the Apache 2 license.)

  • Tivoization: Under the GPLv2, a vendor may sell hardware that embeds GPL software. They need to offer the source code. But they can prevent modified versions from running on that hardware, which runs against the Free Software Definition. This loophole was closed in the GPLv3.

  • DRM: A user of GPL software may legally have the right to study and modify the software, but may be prevented to do so by technical means (DRM). Circumventing these technical barriers is illegal in many jurisdictions. The GPLv3 states that GPLv3-licensed software cannot be part of such a technical barrier, and that circumvention of any barrier “protecting” GPL software is expressly allowed. (This makes it impossible to distribute GPLv3 software over app stores that require DRM.)

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  • Thanks, so the four essential freedoms are part of the GPL v2 license then? – Bill Richard Dec 3 '17 at 19:15
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    @BillRichard No. The Essential Freedoms are just a philosophical fundament for the Free Software idea. But the GPL in all its versions tries to express this philosophy in legally binding language. As discussed in my answer the GPLv2 has some loopholes so that it's possible to violate the freedoms (and therefore the spirit of the license) while still fulfilling the letter of the license. And what the license says is the legally relevant part. – amon Dec 3 '17 at 19:20
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    @BillRichard Note also that the GPL has requirements that go beyond the four freedoms (e.g., copyleft), and there are plenty of licenses that do respect the four freedoms that are GPL-incompatible. The four freedoms are just a baseline philosophical test to determine if a license is "free" or not. – apsillers Dec 3 '17 at 23:36

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