Did you read the Launcher as a local server RFC?
The purpose of the local HTTP server is to allow app developers to easily make API requests to the Launcher.
For example, here is the NFS API. There is also the DNS API and the Authorisation API.
You can use any language or framework you want to build apps, you just need a way to make HTTP requests to Launcher’s local HTTP server.
Think of the applications as being client-side only. There are no servers. You can’t install PHP or MySQL on the SAFE Network.
You need to build a client-side application and interact with the SAFE Network using the local HTTP server. You don’t need MySQL because you can use the SAFE Network itself as a database (via the NFS API)