If Firefox blocks DejaClick locally, you can bypass the issue in the local browser settings. Make note of the consequences however before you do so. Here's the process:
1. Open Firefox and Browse to 'about:config'. You must click 'I accept the risk!' to proceed. Be very careful about all changes going forward from here.
2. In the search box, look for extensions.blocklist.enabled
3. Double Click the item to change the value from true to false
4. Restart Firefox and DejaClick is available.