Re:Why I replaced MIT with copyleft license for Nodemailer
by tomprince on Thursday February 02, 2017 @10:15PM
(#13557365)
Looking closer, you can't incorporate GPL code in a EUPL project, but you can incorporate EUPL code in a GPL project. The EUPL explicitly is allowed to be used as part of GPLv2 project, and indirectly as part of a GPLv2 project via the CeCILL v2 licenses which has a similar provision.
https://joinup.ec.europa.eu/software/page/eupl/eupl-compatib...
Dual-licensing under the EUPL and GPL, with the option to choose either, would be helpful. Otherwise Nodemailer is incompatible with the majority of other copyleft code.