I can do anything I want
except that which the law specifically forbids, because I
own it. The fact that my copying it would violate copyright law does not make me stop being the owner any more than the fact that my beating someone over the head with it would violate laws against assault.
Indeed your statement "you cannot plagiarize its content or distribute it in anyway" is essentially just a tautology because it implicitly means "you cannot (legally) plagiarize its content or distribute it in anyway" -- or in other words, "you cannot legally do [things which are against the law]." Breaking the law with something is illegal, regardless of whether you own the thing in question or not.
If I have a CD with Microsoft Word on it, there's nothing Microsoft can do to stop me from using it as a support to level my coffee table, despite the fact it was designed for nothing of the sort. Obviously if I somehow get hurt they're not liable since I'm using it in a way completely detached from their design and expectations, but I can do it because it is my property and I can do what I want with it.
'Licensing' is a business model that attempts to circumvent the limitations of copyright law, and its use is somewhat orthogonal to copyright. To quote the very article you linked "You automatically own
the copyright for any software you develop." (emphasis added). Not 'You own any software you develop'. What you have is a
copyright, that is, the exclusive right to reproduce and distribute the program (which you can then extend to others, and with limitations such as the first sale doctrine). The specific copy of the program under discussion, however, you no longer own once you exercise that right by selling it.
And if you think that just because you 'license' that you aren't selling the program, then you'd better not be doing so in the EU because that's explicitly not been the case there since 2012. To quote the Advocate General:
(emphasis added)
The European Court of Justice agreed, holding quite clearly that the sale of a 'license' entails the sale of the copy of the program as well, and that a download is functionally the same as sale through a physical medium for these purposes.
In other words, if it looks like a sale, has the time period of a sale, and is charged like a sale… then it's a sale even if you call it a license. If you don't want it to be a sale, make it a subscription so it's time-limited and not a one-off fee (surprise surprise Rockwell is now pushing subscription as their licensing model).
For those who want further details, the case is C-128/11, UsedSoft v Oracle, where Oracle tried to sue UsedSoft for copyright violations because they were reselling licenses. The Bundesgerichtshof (Germany's highest court) asked the ECJ to weigh in on (in simple terms) whether a license holder downloading the program counted as the 'first sale' and if the license was then re-sold the new owner could then download it from the internet (assuming original owner has erased his copy).
As a result of the case it is now clear in EU law that software licenses and the accompanying program are
indeed like eg books -- once sold they may be re-sold regardless of the license terms (ie if the license says otherwise that portion is illegal and thus unenforceable), with the caveat that multi-seat licenses cannot be broken up (eg if you buy 50 seats but only use 40, you can't re-sell the other 10).
For anyone who wants to wade through legalese, (it's not that bad as such things go)
here is the ECJ judgment, and
here is the Advocate General's Opinion from which I quoted.
We'll see whether the US courts follow suit. In theory they should because, again, copyright is
explicitly not a property right in the US.