In the US, the First-Sale Doctrine won't apply to software (unlike tangible books and records) so you probably do not have the right to sell your copy of this software to another person.
Since that's not true ownership, I think it can only be described as a license.
But I'll agree that all sorts of shenanigans can, and often do, hide under that generic term. However, "buy" could suggest many substantial rights that are not on offer (most importantly distribution), so it's a bit of a quandary.
The phrase "Buy Now - $9.99, yours forever" might thread the needle. The sale page would still need to include all the legal terms, of course. I think "license" is a necessary word there.
Not sure how first sale affects software sales other than software rental in the USA is an exception to the first sale doctrine. Software rental is not allowed unless it's a physical video game copy for a video game console or you have a physical copy of the software and you can't just easily make a copy of it in the normal course of using it (not sure exactly what this would mean, but presumably things like software for embedded devices). There are exceptions for libraries and educational institutions.
I am not a lawyer, however.
A perpetual, irrevocable, lease could be a thing.
I know it's pedantic, but to me the key thing is that it is the rights themselves that are "licensed." Not specific copies. The license covers what ways you are and are not allowed to make more copies (that aren't just your personal copy). So e.g. Open Source/Free Software/Closed Source libraries can be "licensed" and copies of them can be modified and included in work you create according to the license.