DORiE is to be released, and should come with a license. There are two options:
GPLv3: Easy license, which requires modifications of the source code to be distributed under the same license. Also used by DUNE. However, DUNE comes with a runtime exception, allowing for runtimes compiled from it not to be licensed under GPLv3. Moreover, DORiE does not modify DUNE code, so we are in these terms free to distribute the source code under a different license.
MIT: The simplest license which just requires redistributors to include license and copyright notices.