If you mean running inside a web page, the answer is no.

Applets made with processing can be viewed inside a browser (you still need java) because they're java code wrapped around a standard java applet (which contains processing functions, just like a library).

Devachan uses python - which doesn't have a builtin graphics api - and opengl for hardware accelerated graphics. Devachan is just a 3d graphic library for python, written in c upon opengl.
You can compile your program as an application (using py2exe) or invoke a script via the command line.
You can talk with the internet using python stardard tcp/ip libraries and use any other python library with it, for sound, reading and writing to disk and everything else.

A devachan plugin for browsers is possible, but it's not on my priorities. I'm developing devachan alone, in my spare time, for free (still no donations). I really just update it when I need some new functionality.

Anyway, for web based works processing is the best tool. If you are interested in making standalone applications with 3d hardware accelerated graphics you can give devachan a try.

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