For medium trust environments there is an option to build and cache bundles in-memory so that you don't need write permission in the application's working directory. An example of setting this up for an ASP.net MVC project can be found here. For a WebForms project the asset controller would just be replaced with an HTTP handler.
Until we set up a new download site (github recently removed the downloads section, though you can still access it for old versions) you will need to build from source or install via NuGet.
The build is generously hosted and run on the CodeBetter TeamCity infrastructure.
We also get great tooling support from the kind folks at JetBrains