We have started experimenting with publishing fatjars. This is still very much subject to change, but if you’re not afraid of breaking changes (in the publication method/location; this is not a comment on the maturity of the components themselves), you can help us test the new setup.
Starting with snapshot 1.2.0-snapshot.20200520.4228.0.595f1e27, you can find the JSON API at
https://daml-binaries.da-ext.net/json-api/http-json-1.2.0-snapshot.20200520.4228.0.595f1e27.jar
You can append .asc to the filename to get a signature file (same as for the release artifacts on GitHub; see install docs for how to check those). We may start publishing more components that way in the future (or stop altogether; as I said, consider this very alpha at this point).
Alternatively, if you are not concerned about JAR file size or code bloat at the moment, you can change the default main method of the daml-sdk jar to create a standalone tool as I explained here. You can check here for a list of main class for each app.