Free and Open Source unhosted web apps

App Direct Link
Swagger Editor Design, describe, and document your API on the first open source editor fully dedicated to OpenAPI-based APIs. The Swagger Editor is great for quickly getting started with the OpenAPI (formerly known as the Swagger Specification) specification, with support for Swagger 2.0 and OpenAPI 3.0.!/?import=
Swagger UI allows anyone — be it your development team or your end consumers - to visualize and interact with the API’s resources without having any of the implementation logic in place. It’s automatically generated from your OpenAPI (formerly known as Swagger) Specification, with the visual documentation making it easy for back end implementation and client side consumption. is a free to use online diagramming application. Needs proxy!
FREEBOARD is an open source real-time dashboard builder for IOT and other web mashups. A free open-source alternative to Geckoboard.
My Mind is a web application for creating and managing Mind maps. It is free to use and you can fork its source code. It is distributed under the terms of the MIT license.
mapshaper is a set of tools for editing Shapefile, GeoJSON, TopoJSON and CSV files . It is distributed under the terms of the MPL 2.0 license.
jsonlint A JSON parser and validator. It is distributed under the terms of the MIT License.
JSON Stat Explorer The JSON-stat format is a simple lightweight JSON format for data dissemination. This is an exporer for that data, the project is under Apache license,
NoteSelf is your personal, private, customizable, Evernote-like experience. More here.
SVG Edit is a fast, web-based, JavaScript-driven SVG drawing editor that works in any modern browser.  
JSON Editor JSON Editor takes a JSON Schema and uses it to generate an HTML form. It has full support for JSON Schema version 3 and 4 and can integrate with several popular CSS frameworks (bootstrap, foundation, and jQueryUI).  
These are javascript only apps that are hosted as static files. You can host them anwhere. They can even run locally on your desktop using a local webserver. Clone this github project to start. Thejesh GN