You are allowed to use the official logo to present, test, review or promote MetaModels as a product. However, you are not allowed to use it for your own MetaModels products and services, because it would give the false impression that they were part of the official MetaModels project.
Own websites on the subject of MetaModels, which are not part of the official project, can use the community logo. You are never allowed to modify the logo in terms of color or graphics. You must not create further variations or modify an existing version in terms of color or graphics. Of course, resizing the logo is permitted.