How does a trademark work?

Can an open-source tool's trademark be used in a fork or other derivative work?

• Take the trademarked term "Chromium" for example.   Can  a derived work (e.g. a "fork" of the code base) use the word in its domain or product name (e.g. "BetterChromium")?      chromium.org's contents are licensed under Creative Commons (http://chromium.org).   Chromium's source code is licensed under an open-source license as well (http://src.chromium.org/viewvc/chrome/trunk/src/LICENSE?revision=37348&view=markup).   IANAL, but I don't think either of these confer trademark rights.   So would a derivative work not be allowed to have a derivative name?

• Answer:

  A trademark can only be used with permission of the trademark holder. If you want to release BetterChromium, you'd better talk to Google first, but I would be wildly surprised if they allowed you to use it. You could, however, take the view that the "ium" ending was not specific to that product, but a generally used form (as a result of being a standard ending for a nominative singular second declension latin noun.) You then might take the view that you'd just make up a front bit of the noun - so end up with something like "heptillium" (the fact that heptillium has zero Google hits isn't absolute proof, but a pretty good clue that the word would be available as a Trademark.) [Actually, once Google have indexed this page, it probably WILL have Google hits!]