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If I build a smart bomb with Linux inside, is it enough to put the GPL text in the firmware to comply with the GPL if I drop the bomb?

I reckon that when I sell my bomb to the military, they are entitled to the source code alright, per the GPL.

But what about the unwilling recipient of the exploding ordnance? Would any survivor be entitled to receive the corresponding sources?

This would be using the GPL v2.

This sounds as a silly question but I still found it fun to ask: it talks about the important lack of restrictions in the field of use.

Note: I do not build any bomb. And I never intend to do this.

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    BTW, the answer might be different if you just "drop the bomb" or "sell" or "provide" it.... – Basile Starynkevitch Nov 22 '17 at 12:43
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    How is the fact that the device is a bomb relevant? The obligations are the same no matter what type of device you distribute that includes GPL software. For GPL software in firmware there are likely to be different obligations for GPLv2 vs. GPLv3, so also you need to consider which version. The Linux kernel is GPLv2 but accompanying user mode applications may or may not be. – Brandin Nov 22 '17 at 12:55
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    This depends on whether usage of Linux in a dropped bomb would be distribution or use other protected rights such as the right of public performance. If the bomb never leaves ownership of the faction dropping the bomb, then arguably no distribution has taken place. But discussions on who owns dropped ordnance are certainly out of scope for this site. – amon Nov 22 '17 at 13:32
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    IIRC, Free (or some other Internet provider in France) was on trial because it was renting an Internet box with modified GPL software (and not publishing the modification). So IMHO ownership is important. But IANAL (and I forgot the details about that trial in France) – Basile Starynkevitch Nov 22 '17 at 13:42
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    For this to be a good silly question, there needs to be something more. For example, if a foreign military drops the bomb and it doesn't detonate for some reason, would the local government be entitled to write a letter to the attacking nation to get the source code (Under GPL, you normally must supply at least an "offer" of the source code, if not included in the distribution)? Would they need to supply security keys (this part may depend on GPLv2 vs. GPL v3). What international court would enforce a requirement of such an offer? – Brandin Nov 23 '17 at 7:46
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If you make a device and use it yourself, you have no obligation to share the code and documenting your changes in the code would be your only obligation. If you give the device to someone else to use, then sharing the code and displaying legal notices comes into play.

The gplv2 states -

If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License.

So for gplv2 the firmware will at least need to contain legal notices for display. It doesn't have to be the full gpl text, you can give instructions on where to read the full license, similar to the short per file gpl header.

So if there is no UI, say the device only responded to commands recieved wirelessly, then you may be able to not include legal notices on the device.

Having said that - for this particular use, it will be a matter of can you be prevented from complying with the license? Those that want you to share the code will not care for legalities and those that care for legalities will be preventing you from complying with the gpl and the gpl terms will be the least of your concerns.

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    Tivoization refers to a slightly different problem: properly disclosing source but preventing modified versions from running on that system by having the system verify a signature, e.g. using a signed bootloader. – amon Nov 22 '17 at 15:53
  • amom is exactly right about Tivoization. To add another perspective... In theory, GPLv2 should allow someone access to the source code, instructions on how to compile, and instructions on how to install the software. However, other software/hardware restrictions on the system, unrelated to the GPL software, may prevent you from updating the software on the embedded device. amom's example of a bootloader signature is an excellent example. Another example might be a security key, or only being able to update when you use a specific password. – airfishey Nov 22 '17 at 17:14
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    What if the bomb is a landmine? Wouldn't the person who triggers it by stepping on it be a user of the software? Shouldn't he receive the text of the GPL to inform him about his software freedoms while getting blown to pieces? – Philipp Nov 23 '17 at 14:13
  • @Philipp - no more than a viewer of a webpage would get the source to the webserver – Martin Beckett Nov 23 '17 at 17:34
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    @Philipp - you must post legal notices as part of the UI, so around the switch you have imprinted "use of this device implies agreement to the terms of the gpl", not your fault if the user doesn't look for or read the ui messages. ;) – sambler Nov 23 '17 at 22:38

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