I think it would be helpful to distinguish between discussing code that achieves a particular result (the source code or executables for, say, bitcoind) and the output or results of using that code.

There should be no argument that Excel, the spreadsheet, is subject to copyright. And there should also be no argument that, if I use Excel (or some other computerized tool) to calculate the result of an equation or expression, that the result is not subject to copyright by virtue of the fact that I used copyrighted code to create it, versus working it out by hand with pencil & paper.

I do not see a meaningful difference between a simple equation and a complicated one - I suspect that all of us would easily agree that "2 * 2 = 4" is not subject to copyright; I find the idea that "342972134893249 * 212312389547523 = 72817233507401087375017372227" is not copyrightable a tiny bit more uncomfortable, since obviously there's more work required to reach the result, and that's not exactly an equation that a lot of us wander around with at the tip of our tongues. But I can't come up with a principled legal reason to distinguish between them, that's meaningful in a copyright sense, since it's well established that copyright is intended to protect creative expression, not sweat-of-the-brow hard work (see, e.g., Feist v. Rural Telephone).

(People unfamiliar with copyright may want to be aware that while a particular number or fact is not subject to copyright, a collection of numbers or facts that has been deliberately arranged/edited/curated can be, but only to the extent of that human creative intervention. Similarly, a creator can take something which is not subject to copyright and add something to it, and the resulting combination is copyrightable. So I can't hold a copyright to Plato's Republic; but if I came up with a new translation of it to English, I could copyright that; or I could take a public domain translation and intersperse commentary and artwork that I created, and get a copyright in the resulting work, but only to the extent of my additions/changes.)

So I am curious to hear more about the argument that BTC could be protected by copyright - either the private keys ("wallet"), or the abstract idea of value which is represented on the blockchain and is controlled by the keys. The private keypair, as far as I know (and this is bumping up against the limit of my understanding of the technical side of BTC/Bitcoin) is simply a group of numbers that happen to have a particular characteristic; they were identified through an iterative process by which potential candidates were created randomly and tested for having that characteristic, and the first which were found to have that characteristic were selected. So I don't really see any of the traditional creative/editorial input from a human being which has historically been an essential part of the creation of a copyrightable work.

Of course, it would be possible to argue that the creative/editorial input was added at the time the program was written, in the description of the criteria for identifying viable private keys - but that suggests that all of our BTC's are the property of the development team, since they're the ones who provided that input.

(Of course, this would be different in the case of vanity addresses, since the holder of the address made a deliberate choice about the text they wanted included in the address. Most of the addresses which are short enough to be found this century are also probably short enough to be uncopyrightable, but at least it's the beginning of an argument.)

I am not wild about calling the blockchain a contract from a legal point of view because it's not at all clear to me who the parties are, or what their agreement is, or what the terms of the contract are. We could say that all of the activity for a day or a week or a year or all time on, say, the NYSE is one big multiparty contract - but I'm not sure it really makes any sense, or that it helps us much, or has any real meaning.

In many ways, Bitcoin is reinventing the Torrens title system, except that the underlying good is an intangible shared expectation of value, not real estate; and there isn't one central registry, but a decentralized peer-to-peer registry.