There are two tasks in adopting libnjb, and they can be pursued independently of one-another. One is to re-package libnjb, listing yourself as the new maintainer. The second is to apply to become a Debian developer. The "new maintainer" process is not difficult, but the queue can be long, so I suggest putting your name in the hat sooner than later. The application is here [1]. I'll advocate for you.
To change the maintainer of libnjb to yourself, install the package `apt-src'. Run `apt-src install libnjb'. Modify `debian/control' to list yourself as the new maintainer, and add a note to `debian/copyright' noting that you've adopted the package. Install the package `devscripts' and run `dch -i', which adds an entry to the changelog. Add an entry noting that you've adopted the package. Run `debuild', which builds the package. Run `debi', which installs the package you just built. Test the package. Send the resulting .dsc and .diff.gz file to me. I'll inspect the package, sign it and upload it to Debian. This process is known as a package sponsorship. Once you've become a Debian developer, you'll sign and upload your own packages. I hope all this hasn't scared you off! Cheers, Shaun [1] https://nm.debian.org/newnm.php