I can’t say that I will never develop on libdmtx again, but this, of course, will not be in the near future. I simply do not have extra hours to even keep up with the correspondence, not to mention any significant development.
So, if you want to fork it, you have my blessing. :)
Unfortunately, I do not know about any other open source packages that perform the same actions as libdmtx (which is why I created it in the first place), but I tried to list any similar projects that I encountered in http://libdmtx.sourceforge.net/resources.php
Good luck