Mozilla review of 0.9.9 said:

This version didn't pass full review because of the following issues ... you need to correct them to get full approval. Thanks.

4. Your add-on creates the following non-namespaced variables in the global namespace, which could cause compatibility problems with other add-ons:

FileUtils NetUtil SCRIPT_ADDON_TYPE ScriptAddonFactoryByScript ScriptAddonReplaceScript