As far as I understand, the main difference between HTMX and datastar is that HTMX uses innerHTML-swap by default and datastar uses the morph-swap by default, which is available as an extension for HTMX [1].
Another difference is that datastar comes with SSE, which indeed makes it server driven, but you don't have to use SSE. Also datastar comes with client-side scripting by default. So you could say the datastar = integrated HTMX + idiomorph + SSE + Alpine.
As far as I understand, the main difference between HTMX and datastar is that HTMX uses innerHTML-swap by default and datastar uses the morph-swap by default, which is available as an extension for HTMX [1].
Another difference is that datastar comes with SSE, which indeed makes it server driven, but you don't have to use SSE. Also datastar comes with client-side scripting by default. So you could say the datastar = integrated HTMX + idiomorph + SSE + Alpine.
[1] https://htmx.org/extensions/idiomorph/