What are the alternative ClojureScript frameworks?

Some of the alternatives are:

For comparison also take a look at the list of different TodoMVC examples at https://github.com/gadfly361/cljs-todomvc.

Is view model an integral part of Carry architecture?

No, but it's a convenient UI pattern to follow because:

That's why it was enforced in carry-reagent package.

Is there a way to code a view model if I don't use Reagent?

Yes, there's a number of tools that can do reactive/dataflow/structured computations:

Is using core.match required in signal/action handlers?

No, Carry doesn't care how these functions are implemented. They can be driven by multimethods or a simple cond. But using core.match seemed to me like quite a flexible and readable solution.