tldr; Probaly ain't happening anytime soon.
I'm gonna chime in briefly. All zone content ultimately is technically copywrite the respective builders. And while I doubt many creators of zones would actively seek reparations for unauthorised use of their content, I believe the general notion of senior staff would be that if the source code is ever released, in any shape or form, that zone files would not be included. Copypasting zones over from your own personal logs or while connected is possible, but relative non practical and is not to be construed as an authorised use of anothers IP.
I think that what you're asking for is a stock diku release, which you can obtain from dikumud.com, although looking at the source tree, you're better bet is to go for one of the publicly available derivatives.
When you say no one owns the source code, you are assuming there are no forks. As early as the initial build of diku I see the following annotation in dikumud.com's FAQ:
[slightly out of context, but....anyways]
+ Problem in the init_socket. The ports do not seem to clear
freely, so you end up with a lot of port binds. Here is a
patch provided by Dean Gaudet <dgaudet@arctic.org>
int init_socket(int port)
{
int s, sbuf, opt;
struct sockaddr_in sa;
struct linger ld;.... and so on.
[end block quote]
So, at the very least, assuming the VERY first patches to diku for arctic would have been applied by dean gaudet and other early imms, the notion of forcing a 9th or 10th generation administrator to release the source code is probably moot.
In all honesty asking kindly, respecting of, and allowing the decision to be made by whoever the final overlord happens to be (at some point in the days years or decades to come) whether or not to open source the actual diku-derivative engine is probably your best bet to see it.
A frivolous law suit would probably only garner you at a maximum a copy of stock diku code, especially if you have no proprietary code (CODE, not content) that is used currently in the current build of the game. I think this is why overlords and people with global read/write access on whatever SSH server is used are somewhat limited.
Anyways, done chiming in.