Is this just straight javascript? I feel like I'm being conned.

Yes, we're using them both together in production and they complement each other really well

Agreed, people are starting to call htmx, alpinejs and tailwindscss the "HAT" stack. They all play well together, and make HTML the primary medium for building your web app again, each satisfying something I am calling Locality of Behavior[1].

A more direct competitor w/ Alpine (although I view it more as a replacement for jQuery, since there is no reactive aspect to it) is https://hyperscript.org. It's a much more speculative project though, for the brave and/or slightly crazy only.

[1] - https://htmx.org/essays/locality-of-behaviour/