I see a bunch of folks confusing first sale doctrines, contract law, etc here, so let me give a very short generalized primer:

1. The first sale doctrine is exhaustion of a single right of the exclusive copyright rights. In particular: It states that the right to restrict distribution[1] terminates upon first sale. It's codified at 17 USC 109, and states: "... the owner of a particular copy or phonorecord lawfully made under this title, or any person authorized by such owner, is entitled, without the authority of the copyright owner, to sell or otherwise dispose of the possession of that copy or phonorecord. "

As mention, this is exhaustion a very specific right of copyright, and applies to copyrighted works. In this case, that would be software. It has literally no bearing on a contract as part of the sale of goods, or whether you can sue for breach of that contract. It is a defense to copyright infringement.

To whit:

If I sell you a book, as part of a contract, and that contract says "no resale", and you sell it, the first sale doctrine would probably[2] prevent me from winning a lawsuit for copyright infringement but not prevent me from winning a lawsuit for for breach of contract.

2. Sales of tangible goods in the US are covered by the UCC (uniform commercial code). Every state has passed a version of the UCC (though not all are on the same revision, for this discussion, it doesn't really matter).

The UCC lets you freely contract for almost anything. It fills in and has default terms when not stated, requires some contracts be in writing, etc, but there is generally nothing that prevents you from doing something like preventing resale of an object. You can argue it's unconscionable to a court, or you can argue it violates some other law (antitrust, whatever), and thus the court should not enforce it but in most cases, it'll be a valid and enforceable contract on its face. In general, if you have a legal right to do something, you can validly contract to forgo that legal right. For example, you can promise to not marry anyone until age 30, promise to marry someone in exchange for money, etc (Neither of these would be UCC contracts)

3. As a final note, for sales of UCC goods, there is no additional consideration necessary for them to modify the agreement, only the general requirement of good faith.

I offer literally no opinion on the status of this particular agreement, or anything like it. The above is also not legal advice (among other things, i've left out exceptions, and merchant <-> merchant rules, and ...), just an attempt to clear up some common misconceptions.

[1] "to distribute copies or phonorecords of the copyrighted work to the public by sale or other transfer of ownership, or by rental, lease, or lending;" Note that "distribute copies" does not mean "make copies", it literally means "distribute" an already made copy. Reproduction is a separate right.

[2] There are some current cases (and past ones) making arguments that you can contract away your first sale rights. The problem with this idea is that as titled and written, 17 USC 109 is, IMHO, not an affirmative right (and thus something you could agree to forego, even though some cases hold it must be pleaded as an affirmative defense), but instead a limitation on the exclusive rights the owner has. It's even titled " Limitations on exclusive rights: Effect of transfer of particular copy or phonorecord".

This is why the standard mechanism software companies attempt to use is to classify their agreements as licenses that do not transfer ownership, rather than sales that do. If you are not an owner, the first sale doctrine does not help you. Success varies in ability to convince courts they aren't selling software, but instead, licensing it. In the end, it may not matter if they can succeed by suing for breach of contract rather than copyright infringement :)