From Slashdot:
slummy writes " JS/UIX 'is an UNIX-like OS for standard web-browsers, written entirely in JavaScript (no plug-ins used). It comprises a virtual machine, shell, virtual file-system, process-management, and brings its own terminal with screen- and keyboard-mapping.' If only you didn't need an OS to run the web browser on."
http://www.masswerk.at/jsuix/

Would this be useful on the PSP since it would run from the browser?

(It would seem that the site has been "slashdotted", it will probably be accessable in a few hours)