Currently we use a slight fork of (an outdated) JSON-Spirit (http://www.codeproject.com/KB/recipes/JSON_Spirit.aspx) in our repo. The debian maintainer for Bitcoin asked me a while ago (and I never got around to filing a bug report for it) if it were possible for us to revert back to the original version so that it is possible to use a packaged version. To do this, we need support for forcing numerical output to do fixed-length output of reals (see http://www.codeproject.com/KB/recipes/JSON_Spirit.aspx?fid=448567&tid=3909548 and scroll to the bottom to read a brief thread on the subject, it would be much appreciated if someone could take up that topic and continue with this issue).
As much as I prefer avoiding forking, there's little to no benefit in this case as JSON-Spirit only provides/supports static linking...
Hence why its really not an important issue, its just something that would be nice to do eventually (there isnt a JSON-Spirit debian package right now anyway...)
Looks like a json-spriit package in Debian exists now: https://packages.debian.org/zh/source/sid/json-spirit
Not that we can use it, as our custom changes to the library are extremely important as long as floats are used for monetary values...
After the RPC redesign, if we decide to use strings instead (see also #3759), we can revert to the system package.
Looks like we're rather going to move away from JSON-spirit completely. Closing in favor of #4738.