[amper5and]

There's no caveat. It says "Redactor распространяется бесплатно по лицензии MIT или GPL, на ваш выбор." which literally means "Redactor is distributed freely under the MIT or GPL licenses - it's your choice."

Edit: This goes to the lack of English docs, not to your misunderstanding I'm sure.

[drewmclellan]

In the source of the script itself, it has:

    Dual licensed under the MIT or GPL Version 2 licenses.

...which is how jQuery is licensed, as is common for plugins and other jQuery-based projects.

[bdfh42]

Interesting - the text with regard to the licensing changed between my first and subsequent visit - now clearly licensed as you say.