My thoughts....
When it comes to old abandon-ware, there is no-doubt you are doing a good thing.
But when it comes to re-hosting work by an author such as Hourences, or any author that is still around and still hosting the original files, I think you are doing them a dis-service by not sending visitors to them, or mirroring their files in the same form you got them in.
I have noticed a change in attitude over the years in the way we share our stuff online.
Once upon a time, we supported each-other by linking to the source of our inspiration or material.
Then we then got used to visiting 1 mega-site for everything, as sites like PlanetQuake became big. People were even dumb enough to rely on sites like this (and still do), to provide all their project and clan hosting needs.
Since then many community members have tried to host a massive database of files (UT-Files is a good example), and we get used to the convenience again. They then become far more important than just convenient.
Until it is gone.
No-one plans to let everybody down, but sh*t happens, and this game has been around a lot longer than anyone planned for.
By then no one has any idea where the original sites were, and often they are long gone, as who keeps on hosting a site with few visitors and no feedback.
I actually got a very happy email back from the owner of an old (and still going) texture site, that specialises in hosting dead projects.
Even though I was sending a list of broken links, they were just happy someone was actually using the site, rather than just ripping the contents for their own site.
Having an important service that people start with is great, but it does not have to be where a visitor ends their quest.
The Dane's mega texture resource could easily be a gateway to an even bigger world of textures, tutorials and tools.
eg. Your database could still contain the thumbnails, but send a user to Hourences texture pages etc.
1) This saves you a little work and bandwidth.
2) This bypasses any issues of licence.
3) Stops the needless duplication of resources.
4) Often earns you a return link from their site.
5) Often gains you a new friend.
I have contacted several ex-developers that have all had open attitudes with their work, so there has never been a proper base-distro. This made it hard to first find who made it, and if they had made any more.
The deco packs by William Sherriff, bobkakabk and GiGGsy are a good example. individually handed around over the years without a please or thank-you, like a child at a pedo's party
The William Sherriff collection is now all complete and all available again, only because I bothered to look for this William Sherriff person , and discovered he had made far more packs than I first knew about.
Each of the new downloads I provide contain some info on William Sherriff, some example images and a copy of the old Spooger page where his work was originally hosted.
The same goes for the other authors I found.
Far more work went into hunting all the files than most people would do, but I enjoy the detective work.
However
There are many other files I have that are worth sharing, but will not until I know I have the right to, as I do not have a "distro".
I may not need any permission, but I cannot, and will not assume that, until I have read something that says so.
That is why I never share cache-ripped content until it can be a full distro again. I can then include the original permission of "do what you want" so the next person actually knows what they are allowed to do.
If the best you can do is credit the maps that the resource is known to be used in, especially with old stuff, that is as much as you can do
I am not so dumb as to expect anyone to be able to tag your entire collection, but think of it like this;
If an unknown texture stands-out, and there is also a good map that you know it is used in, why not list it as an example anyway?
The best way to check a texture is to see it in use (and the maps you make would be a good start
).
We do make every effort to promote free resources, but also every effort to make sure that in another 10 years, this site is still going (maybe)
Creavion started the ball rolling on a thread for "Textures for (non)commercial usage" aimed at a more professional attitude (and hi-res textures).
http://www.ut99.org/viewtopic.php?f=8&t=4683
We followed his lead by starting the same for (non)commercial audio.
http://www.ut99.org/viewtopic.php?f=51&t=4745 
...but...
