Ace, like Skywriter is perhaps a solution for a more easy way for programmers to contribute open source projects, because the code editor works online and it is based on an extensible framework.
Skywriter is a Mozilla project whose former name was Bespin, the name of a planet in one the Star Wars movies of the, specifically in the Episode V: The Empire Strikes Back. The planet hosts the floating clouds city that must have inspired the creators of the project.
The new name is a reference to the cloud. The Skywriter project was abandoned by Mozilla as a separate software (but the code is still available for download) to be merged with Ace from the site Ajax.org, another open source project.
Skywriter runs entirely in Canvas, unlike Ace which use HTML components and DOM.
Ace means Ajax.org Cloud9 Editor, it supports editing of code in thirty programming languages, possibly in a collaborative way with GitHub integration when running on Cloud9.
You can easily verify that display and editing are fast while running online, it is easy to use and intuitive. It is also extensible.
Once online, the editor or your own version, will enable programmers to contribute to a project and modify the code of a file, anywhere. That can allow to work on the code at any time - on the train, a waiting room. This also allows contributions to code in real time for an open source software.
Ace may be integrated in Drupal for code editing, but in addition to the common editor. Wordpress using TinyMCE, moves to the CodeMirror competitor which becomes the core of this tool since version 4.
Ace is the editor of Advanced Explorer.
ACE is under the BSD license.
CodeMirror is another editor for programmers, free and open source which supports 60 languages. CodeMirror uses HighLight.js to improve readability, a tool that may be used in a web page, and actually is used on this site.
It offers auto-completion, code contraction (folding), some syntactic checks (not as developed as in NetBeans).
The themes of Highlight.js all look alike, but it is possible to customize one fairly easily, and obtain for example the look of SyntaxHighlighter if you prefer.
It is embedded in Light Table (see the list of IDEs in the programming section). Since version 4, TinyMCE uses CodeMirror too.
Brackets is an open source editor developed by Adobe that works in the browser. Although it is based on an existing software, CodeMirror, it is in 2014 still under active development. It relies on CEF3 to integrate Chromium, while LightTable use node-webkit.
It is oriented to contextual tools to provide a clean display. The edited code is synchronized with the display in the browser, the source with the presentation, it is called "live editing". But this does not work if the page uses a template, unless to create an extension to support it. Some complaint also it is broken. Moreover the editor may be too slow on large files.
Amounts of videos are provided to introduce the software.
See also the list of development environment.