Can I (proactively) prevent someone from leaving me something in a will? What can I do to prevent someone from leaving me something in their will? Generally speaking, in North America: Do I have to take responsibility for things left to me in a will or are their other options?
What can I do to prevent someone from leaving me something in their will? Nothing. Allowing other people to legally change someone's will defeats the purpose of a will: To express the writer's last wishes. (That is why the full title is a "Last Will &amp; Testament"). Do I have to take responsibility for things left to me in a will or are there other options? No! You do not have to accept an inheritance. The legal process for rejecting an inheritance is called "disclaiming." It happens often enough that there are plenty of nice summaries of the process on-line. Your next step should probably be to read one of them.
There is not uniformity of law on this question, which is usually decided in the period after a death, but before a will is admitted to probate or an executor is appointed (typically in three to five days). As a result, the legal jurisdiction (usually a country or sub-national state or autonomous region) involved matters a great deal. For example, Italy used to presume that you did not want organ donation if you didn't execute a document during life saying that you did, and now has the opposite presumption. Similarly, many jurisdictions used to give a blood relative priority over a same sex partner, but now recognize a civil union or same sex marriage as having priority over a blood relative. Some jurisdictions give you some say over, for example, whether your body's organs will be donated or your body will be used for medical research. Some have formal documents that can be drafted and there are such things as "negative" provisions that are documents saying who cannot do something with your body. Other jurisdictions, as user6726 suggests, have a fixed priority system for determining who is next of kin and that applies strictly. Needless to say, a critical issue is how any such directive would be enforced. Obviously you, being dead, can't do that, and documents don't simply crawl out of desk drawers and walk themselves into court houses after your death either. Your wishes will never be enforced unless someone takes it upon themselves at the critical moment, to take action, and in that case, local law determines under what circumstances that person's statement regarding your wishes will be honored. Often, the person who might step up to take action doesn't learn of your death and of the location of your body until it is too late. If you die in circumstances where your identity is unknown, or where no relatives can be located and no directives can be located, some public official or whomever else ends up in possession of your body (often a corner) will have to decide for themselves what to do without your input.
That all seems perfectly legal, enforceable and, providing everyone had been given legal advice and agreed to it, would not breach a lawyer’s code of ethics. Of course, my response to a child of mine who proposed it would be to rewrite my will to give them nothing - it’s my money and I’ll do what I like with it.
what responsibilities/liabilities does/will his company have given that it's in possession of my property? None. There is no contract (implicit or otherwise) between the owner and you. The owner receives no consideration from you in exchange for storing your goods, and an essential element of contracts is an exchange of considerations. Thus, he has no obligation to continue storing your goods. Another essential element in contract law is that the agreement --meaning the conditions thereof-- be entered knowingly and willfully. Since the time of making the arrangement and up to now, you were reasonably unaware of the likelihood of an obligation to pay the owner. This preempts the owner's right to start billing you. If anything, you would need to prove special circumstances to avail yourself of a viable claim of promissory estoppel. See Havens v. C &amp; D Plastics, Inc., 124 Wn.2d 158, 171-172 (1994): To obtain recovery in promissory estoppel, plaintiff must establish (1) [a] promise which (2) the promisor should reasonably expect to cause the promisee to change his position and (3) which does cause the promisee to change his position (4) justifiably relying upon the promise, in such a manner that (5) injustice can be avoided only by enforcement of the promise. However, the viability and duration of any relief pursuant to promissory estoppel seems very unlikely in the situation you describe. The hardship you are undergoing --and which prompted you to store your goods there-- is unfortunate. But generally speaking, a third party (such as the owner) who is unrelated to the causation or prolongation of that hardship cannot be lawfully forced to aid you for free.
Usually, an attack on the validity or prudence of the underlying order is not a defense to court action to enforce it. Usually, the only exception would be when it was impossible, or practically impossible, to perform the court order for some reason. You could seek to modify the order, but that would be prospective in effect only and usually isn't granted unless there has been a change in circumstances since the original order was entered. You could also bring a motion to set aside judgment (usually this has to be done within six months of entry of an order) on the grounds that this provision was included only due to mistake or irregularities in the process or excusable neglect. But, that only would have only prospective effect.
A deed executed during life trumps a will. The other siblings would have to argue: Your mom did not have the capacity to execute the deed (which is a very low standard in terms of her capacity). The deed was procured from undue influence from you (which requires them to meet a high bar of proof). The deed was really the implementation of an agreement for you to hold the property in trust for everyone (which requires some affirmative evidence of this intent).
The general answer is, no, it is not valid in the US, see this article. Exceptions to laws recognizing e-signatures abound which exclude wills from general laws recognizing electronic signatures. Nevada is the one current exception (conveniently located between Oregon and Arizona). There have been attempts to legalize electronic wills, including in Arizona (SB 1298). Although Tennessee does not recognize e-wills, a gentleman in Tennessee went ahead and did it, and in Taylor v. Holt, 134 S.W.3d 830 the court decided that the will was properly executed and witnessed. Electronic notarization is recognized in Arizona, though apparently for things you file with the government (not things that your heirs will eventually file), whereas in Oregon it is a general-purpose way of getting a document notarized. Since the courts are loathe to completely disregard a person's last will and testament because they didn't narrowly follow requirements, you might be able to "get away with it", but it would not make things easier for the executor.
As Polygnome points out in the comments, the first step is to determine who owns the original copyright on your mother's work now. This will be her heirs. If you are the sole heir then no problem. If the copyright was explicitly left to you in her will, also no problem. If there are multiple heirs and no explicit assignment of the copyright, then problem. The copyright will probably be considered part of the chattels of the estate (i.e. everything except real estate). If those are allocated fractionally (e.g. half each to two siblings) then the copyright probably followed that principle, unless you have already come to some agreement about it. If you are on good terms with the siblings then the best bet is to just make a deal for their part of the copyright. You could just ask them to sign it over to you, or you could cut them in for a percentage of future royalties. That makes the situation 100% clear, and any publisher is going to require 100% clarity before they consider offering a contract. Once you have the whole copyright you can go ahead and register. I've looked through the registration process and it doesn't actually ask about derivative works. What it wants to know is whether you own the copyright, and who were the authors (including works for hire). So just fill it in on that basis.