The Json parsing I've initially attempted was a mistake. I've assumed the XML parsing would be harder than necessary, but I ended up fighting wxPhp's arbitrary Json output (arrays holding objects of different types.. which is no good for D, or my sanity).
Yesterday I've started working on xml parsing instead (using Vladimir Panteelev's xml library) and now I have a full script that parses wx doxygen files in pretty much the same way as the wxPhp script (although the syntax is much nicer to work with). I'm now in the process of testing the entire output to verify that I've parsed the xml files correctly and loaded all the info in the same way as wxPhp's xml script (basically I'm going to do some printf diffs). Once that is done I can begin working on porting the source_maker script (obviously I can skip the Json part altogether since I have the structures in memory already).