A phrase you see often from people with just enough knowledge of the law to realize that if they give advice on the law that someone else acts on, they can be held liable should that advice turn out to be inaccurate.

I am such a person, and your question is one which clearly requires a lawyer for a full answer. (And that answer will probably be "it depends".) But here is my limited understanding.

First of all it is a misnomer to say that a document has a owner under copyright. There may be many people who have some copyright assertion to it. For instance if merlyn writes an article, and then I write a paraphrase, we both have copyright on the paraphrase. Should my paraphrase be copied with modification by someone else, then all 3 of us have copyright on the last document. This can even be true even if no words of merlyn's have been preserved into the third copy.

Does it seem strange that no word of the original survives but the result still has a copyright in effect? Believe it or not the first legal case pursued after copyright was introduced in English had this character! In Burnet v. Chetwood (1720) at issue was whether the executer of Burnet's estate could prevent an English translation of a work published by Burnet in Dutch from appearing. (He could.)

Back to the question. Since multiple people may have copyright on the output, all of the people whose work is part of the output may have a copyright claim. Note the phrase, "part of the output". You may have used tools such as perl or gcc in the production of the output. But as long as what is produced does not include material from them, their copyrights don't extend to the produced work. However in the case of a template system, intellectual property within the template is part of the output and therefore is likely to be covered. Likewise javascript from the backend that appears is also covered. Content remains (unless alternate arrangements have been made) the property of its author(s). And I suspect that look and feel is likewise covered.

So in theory virtually everyone has a right to the output, unless there are agreements saying otherwise. Whether they will enforce that right is a different question. But they have a claim, and if they wish the result not to be distributed etc, they have recourse to the courts.

Incidentally this is why the GPL says in the preamble: <bockquote> Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does. Since a template system includes itself in the output, the output is a work based on the program...