While trying to understand the PlantUML schema license to adopt the right one for my projects, I looked at two projects to have an idea about which version they choosed.
For example the integration wth IntelliJ Idea uses the LGPL version, ok so it's compatible with the IntelliJ itself.
But when i checked the Eclipse pluging I found the GPL version, there is not problem with PlantUML because it has also the EPL license. However in these cases you need also double licensing also for all used library
as stated here https://www.fsf.org/blogs/licensing/using-the-gpl-for-eclipse-plug-ins
It seems to me for example that Ditaa does not have a double license that permit to use it with eclipse. I did not check the other used libraries.
So my question is: is this a violation of the GPL license with respect to the ditaa project or I'm not understanding licensing details?