One reason may be to increase the number of folks using the library. I'm not saying that would happen, or that the original devs care, but it's conceivable, isn't it?
> and you are not in a position to tell them what should matter to them.
I'm not telling them anything -- I'm expressing an opinion and asking questions. [sidenote: isn't it ironic to be called "disgustingly arrogant" and attacked for asking questions on a matter of free speech? I think my discourse has been polite and respectful].
> Nothing on that page constitutes a waiver of GPLv3. It is merely an offer of an alternative license to a subset of potential users.
Perhaps waiver was the wrong word, but lets look at this a moment:
The offer is to everybody (barring a small (arguably dubious (enter lawyers)) subset of potential users, where (again, presumably) the license is more like MIT than GPL.
At any rate, the decision is in the hands of the authors.
 https://news.ycombinator.com/item?id=6614482, https://news.ycombinator.com/item?id=6614179