Under which license are the atlassian plugins developed?

Hey Guys
Can s.o. help me please. I am looking for the license that is defined for confleunce plugins.
e.g. com.atlassian.renderer.wysiwyg.converter.DefaultWysiwygConverter
I would like to use the WysiwygConverter which is from Java Package: com.atlassian.renderer:atlassian-renderer

Have’nt found and information under which license this package is developed or published. Is there a common license everything from atlassian is developed with?