I don't know whether/when the flat and XMLRPC interfaces will be removed, but you should know that neither is maintained anymore (IIRC they don't support the split of friends into read and watch which was one of the first Dreamwidth changes 12 years and change ago (12??? Oh, my. Soon Dreamwidth will be old enough for its own Dreamwidth account), to give you an idea how long they have been), and that a 3rd client interface is being developed. See https://dw-dev.dreamwidth.org/221443.html for (what I think is) the latest update.

Oh, and hi, fellow FreeBSD user!

ETA: IIRC, some of that API is already available on Dreamwidth itself.