Mudita OS-P (Mudita OS-Pure) will be released on the GNU GPL v3 License. We decided to go for this copyleft license so that any forks and changes made to Mudita OS-P (Mudita OS-Pure) will have to be released on the same license (made available to the public) and documented.

Does Mudita OS-P (Mudita OS-Pure) with an Open Source license means anyone can use it on their own E Ink device for free?

Yes, however any changes done to the software need to be released and documented under the GPL v3 license.