Sometimes I think I want to develop a standalone (needing neither a web server nor a browser to run) desktop GUI application for Windows, Mac OS X and Linux using HTML5, CSS and JavaScript to form the GUI.
But as far as I know, both Adobe AIR and Mozilla Prism are deprecated. What are other options for this task?
UPDATE: Responding to the answers and comments already got, I'd like to emphasize that the applications must work on Windows, Mac OS X and Linux without any serious modifications. The platform is to be actively developed and supported for all the 3 major PC OSes. Single-platform applications are not an option, neither are applications with limited support of one of them.
Based upon the solutions evaluated on http://blog.neamlabs.com/post/36584972328/2012-11-26-web-app-cross-platform-desktop-distribution, these should be the most relevant HTML5 Runtimes with regards to your requirements.
- XULRunner - Benefiting directly on Firefox development efforts, this is an extremely well-maintained solution with great cross platform support but with almost non-existant tooling or documentation for packaging and distribution other than those of Firefox and other open source XULRunner-based applications themselves
- Chrome Installable Web Apps - Like a Chrome web app with more desktop integration. No flash support.
- Mozilla Native Web Apps - Like a Mozilla Open Web App with better desktop integration. Still requires online installation through Firefox Marketplace.
- TideSDK (formerly Titanium Desktop) - Although it may appear to be the perfect solution all-round, the current state is that TideSDK is not nearly production ready (may change in a couple of months or so, due to active development)
- node-webkit looks very relevant, not sure about the "production-ready" part though.
One option is to use berklium. It wraps all the nasty chromium stuff and makes it easier to embed browser functionality in your apps.
There's always Microsoft Silverlight (which does have implementations for Linux/etc. if you're concerned about that, as noted on the linked page).
Wait a minute, from what I can tell Adobe AIR is still being developed, with a stable release just this past month. It's only Linux that isn't getting official releases anymore, for some strange reason.
Opera Widgets is also of the kind you are looking for and is also deprecated, but can be turned on in opera:config
as far as I know.