The Joomla documentation states clearly that it's not permitted to use the word "Joomla" as part of an extension name, unless it's called "MyExtension for Joomla!" (except with a license):
The usage of 'Joomla' in extension names or domains listed at JED requires a license by OSM. Extension names must be titled 'for Joomla'. ie: 'MyExtension for Joomla' is permitted. 'Joomla MyExtension' is not permitted. Use of the Joomla version is not permitted. ie: 'MyExtension for Joomla 3.0'
But List B1, item #4 on the same page says:
Extensions that use "Joomla" or a derivative of Joomla in the extension name?
Only if licensed by OSM.
What does a derivative of Joomla mean? There are lots of extensions called Joom Myextension, isn't that a derivative of Joomla?