Does the BSD licence implicitly apply to derived work?

Question

Moved from the discussion of this answer, which makes the following claim about BSD licences:

The 3BSD licence requires (in clause 1) that your copyright notices be preserved, and that some licence text be reproduced, whenever your code is copied. But it does not require that that licence text actually apply to the copy.

However, to me that seems very unlikely to be true, for the following reasons:

• By requiring the preservation of the specific licensing terms, without explicitly saying "those terms are to be included as a reference to the original author's licence only, but should not be taken as binding", it seems fairly clear that the BSD asserts the same licence applies to copies, with or without modification. A licence notice's language specifically asserts that a work is covered by the given licence. That is a face value reading of the notice's language. Requiring that copies carry the same language without saying it isn't binding necessarily asserts the copies are covered by the same terms, set forth by that language.
• If it were true that copies don't need to be covered by the same licence, then the notice requirement would be trivially sidestepped by simply making a verbatim copy, then stating that it was in fact relicensed under a different license that does not carry the same requirement. Since BSD explicitly does not distinguish between copies "with or without modification", that would be perfectly within the rights given. As it's unlikely that such a reading was intended, I think better evidence is needed to support this claim.

It seems to me that in practice, when BSD-covered derived work is incorporated into code under a different licence, it isn't so much that BSD stops applying to it, as it becomes embedded in the other work, and BSD does not prohibit adding further restrictions and terms (licensing and otherwise) to the resulting work, so long as its requirement of copyright and licence notice is satisfied.

Answer 1

The 3BSD licence requires (in clause 1) that your copyright notices be preserved, and that some licence text be reproduced, whenever your code is copied. But it does not require that that licence text actually apply to the copy.

I believe that this quote from @MadHatter is subtly wrong.

Yes, the 3BSD license is a permissive license that allows a recipient to redistribute a (derived) work under a license that contains additional requirements and/or restrictions on the code. But that is, as far as I can tell, not an actual re-licensing of the BSD code and the 3BSD license would still be applicable to that code, in addition to the additional requirements/constraints imposed by the other license.

Therefor, it is more correct to say that both licenses apply to the code, where redistribution has to comply with the requirements from both licenses. This is different from the code being dual-licensed, where the recipient can choose which license terms to follow.

Moreover, as the 3BSD license does not grant the right to sub-license the code, the additional requirements can only be applied in the form of a "secondary license", where that license is used for either some other part of the application or for a modification to the code and the license includes requirements that are claimed to apply to the entire codebase. This means that the secondary license is indirectly applicable to the BSD code and if you can successfully separate the two, then the additional requirements also no longer apply to the BSD code.

Answer 2

I think there's a semantic issue here, which may or may not mask a legal one.

When you make content available to me subject to the conditions of the unmodified 3BSD licence, then I may avail myself of most copyright-controlled rights ("Redistribution and use in source and binary forms, with or without modification"). In return, I have two obligations (the third, to retain from claiming the original author endorses my work, is a requirement that applies regardless of licence):

Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

I must obey those requirements to avail myself of the specified rights. Further, I cannot give others rights I do not myself have, so when I modify the work and redistribute it, I may not fail to place those obligations on the recipient(s). I may, however, add further obligations if I so choose, as I have written elsewhere). Thus, I may convey the code to you on the conditions shown above, plus the conditions that you give me a thousand pounds and agree never to give a copy to anyone else.

The semantic issue is whether you would describe such code as "being conveyed under the 3BSD licence". If you wouldn't, as I wouldn't, then as above it's clearly permissible to take 3BSD code, modify it and convey it on, under conditions which are no longer accurately described by the 3BSD licence, so there is clearly no requirement that it should remain under the licence. If you would describe the code discussed above as still being under the 3BSD licence, then in the way you use that term I agree with you, and there's no question to answer.

The legal issue only arises if you think that the 3BSD licence requires that downstream recipients must be subject to the conditions of the the 3BSD licence and no others (that is, "subject to the 3BSD licence" as I, and others, use the term). You've indicated that you do not think that, so I'll stop here.