I think the publisher should make a useful software to create some private servers after they shutdown their services. mostly that games could still "live" even without the publisher. I mean if they didn't some things will be gone like forever.
Take a game like Star Wars Galaxies, for instance. Sony didn't own the rights to Star Wars; it was licensing them. When it shut down the game, turning the code over to the public would have been a violation of their license and would have gotten them sued.
Now let's take an example of a game based on original IP. Even then, the publisher presumably wants to maintain its control over that IP. It wants to preserve the option to sell new iterations on that IP at some point in the future.
Even in the case of a publisher's going bankrupt or shutting down, it will attempt to liquidate its assets (IP being a key asset) in order to pay off its creditors. (For example: this is how the Terminator franchise keeps surviving in various iterations, despite the bankruptcy of its original IP holder. The rights were auctioned off at fire sale prices, rather than simply committed to the public domain.)
Intellectual property is the entire basis of the entertainment industry, be it movies or games. It is, accordingly, very fiercely guarded.
[Note: this is not a comment about the ethics or the morals of IP, nor a comment on what game companies should do. It is merely an observation.]
ie: At the end of this licensure period, $publisher may make technical game material available for use. These materials do not extend a license etc etc. $publisher may not charge for, etc etc.
Most of the time, these old games will have small user bases, and if not, the licensor should be able to exploit that in some way.
Of course, every license is slightly to significantly different from the rest. So no telling which games involved more liberal or more restrictive terms within their original agreements.
Not sure how that would translate to MMO games though... should we put only the code and design in escrow, or also (parts of) the generated worlds? Player characters? Design tools?
Because of it, two revival projects exist: Eleven (http://elevengiants.com/) and Children of Ur (http://childrenofur.com/).
I only played this game briefly when it was around and it didn't hold my interest for long, but it was a really unusual and quirky game. I'm sure the devs go into more detail somewhere why it failed, but it was likely because of bad timing-- it was a post-Farmville Flash game during the time when mobile gaming and HTML5 were really starting to kick off.
Hopefully if it got popular game companies and crowd sourced games would be "forced" to use it.
Useful commented server stuff would be nice, but the least they could do just drop the server blob and let the community figure it out.
Needing to reverse engineer the servers is the hard part.
It was a incredible adventure, we had to reverse everything from server to client. We made our own tools, reversed each packet byte by byte, maintained a wiki. It took years. I personally learned alot and would love to do something like that again. If only I had time.
One of the best way to learn if you ask me.
Those art assets probably just languish on some backup server. If they're not just completely lost.