You can interact with these forums via email if you prefer.
To subscribe, send an email to firstname.lastname@example.org
The forum/mailing list gateway is two-way, so you can also post in the docx4j forum from your email client using the email address you registered with.
This capability is new, so please advise of an issues.
There is also a docx4j-dev mailing list, intended for people who are working with the docx4j source code. The dev mailing list is not currently bridged to a forum.
cheers .. Jason