Nit: this would be easier to read if the object argument was more structured:

    remote.client.request({ to: remote.webapps,
                            type: "install",
                            appId: appId,
                            appType: appType },
                          onResponse);

That also makes the lines short enough to enable you to call request() directly on this._remote.client without exceeding 80 characters per line, so you don't have to assign it a local variable that then only gets used once:

    this._remote.client.request({ to: remote.webapps,
                                  type: "install",
                                  appId: appId,
                                  appType: appType },
                                onResponse);