What does an ex license mean? That the content is no longer owned by anyone in particular?
To give you a more precise answer, the copyrights for the original manga belongs to the author Nihei Tsutomu. Tsutomu signed away part of his copyright over to his publisher, including the right to manage derivative works (in this case translations) and issue licenses for them. A license in turn, grants the recipient (Viz Media in this case,) the right to certain copyrights. The license was time limited as usually the case. Viz decided that the IP wasn't worth keeping in print and did not renew the license. The copyright has since returned to the Japanese publisher (Kodansha?). Now this means that Viz doesn't have the right to issue a DMCA or to sue anyone because they no longer have any copyrights to the work. The Japanese publisher and the author aren't American/part of the Anglosphere and either do not care or are not aware of the fan tl. Therefore there is almost no risk to keeping this up on the site.