Firefox JSTerm v2 is available.
- performance improvements;
- can undock the terminal in its own window;
- native osx fullscreen support (see screencast);
- global history (shared across sessions);
- better multi-line support;
- added $ and $$ methods;
- more keybindings (see :help)
For Firefox and Addons developers: like Scratchpad, this tool comes with a "chrome" mode (type ":chrome" to enable it).