Anyone can get a free virtual machine (VM) with Ubuntu that has root access, apt-get, and many commonly used web tools. (most services offer this) The virtual machine shuts down after the user has been logged out for 60 minutes, but the state is preserved. Pro plans get an always-on VM.
Once an account is set up and the user has logged in, all that's needed to start is to pick a language, a framework and a PaaS. Codenvy also allows anonymous logins albeit with some important limitations.