Hello! Would just like to add here that http://bugs.debian.org/833256 has been filed and another option than seeking someone to maintain src:shadow would be to migrate over to the tools provided by src:util-linux (which other distributions use and is well maintained upstream) and thus possibly getting rid of src:shadow.
Anyone thinking of adopting shadow might want to investigate this alternative. Feel free to comment on #833256. Regards, Andreas Henriksson