That's assuming you want all your scripts to be loaded on the front end asynchronously which seems to be only for development. For production I think you'd still want to compile this all down for a faster load time. From the jspm page: "For production, use the jspm CLI tool to download packages locally, lock down versions and build into a bundle." So I think you're correct that there'd be no build step for development but you'd still have some sort of script being run, whether it be gulp or otherwise, that builds it for production use.