I'm the creator of htmx and think this is a great library/snippet. Much closer to what htmx-like functionality in HTML would/should look like in that it is following existing norms (iframes, the target attribute) much more closely than htmx.

From a practical perspective, a lot of the bulk of htmx is bound up in things like history support, collecting inputs, a lot of callbacks/events to allow people to plug into things, etc. I expect a lot of htmx-like libraries will come out now that it has some traction: it's not a super complicated idea, and many of them will pick smaller, more targeted subsets of functionality to implement. That's a good thing: the ideas of hypermedia are more important than my particular implementation.