I thought a little info might be helpful.
I don't dare mention the product name... but another open source
product has the following clause in their trademark policy which
allows unwritten licencing of the trademark:
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//Use that does not require a written license//
Non-commercial Products that exist solely to support Drupal and its
adoption, use and users may use the Drupal trademark in promotional
materials, such as posters, books, pins, and t-shirts.
Use of the trademark that is merely descriptive of the Product is
acceptable without need of a license. If such description clearly
separates your trademark from the Drupal trademark (e.g. by describing
the Product as "YourProduct for Drupal"). In other words, you would
not need a license to promote the name "TotalTraining for Drupal" but
branding your product so it seems like it comes from Drupal (e.g.
"Drupal TotalTraining") would not be permissible.
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This policy has allowed the community to build a huge 3rd party
community support network around their product while protecting their
trademark successfully.
Maybe something to consider.
Michael Wheatland