Is UOX legal?
I will try to answer this with my best efforts. Software rights/law hit's my interest but I'm far from expert 
or even educated in it in any way. 

Developing for UOX.... 
is perfectly legal! UOX is a independent piece of software not violate any law. 

Distrubing UOX.... 
is perfectly legal! (As long as you provide source with it) 

Running an UOX server.... 
is (mostly) legal. UOX relies on the .mul files from your UO-client distribution, however these are only COPY 
protected as the name says, not READ protected. Thus an application depending on them thus nothing bad. 

Creating a completly new map (with ie worldforge).... 
is legal. 

Creating a modified map (with ie worldforge).... 
is illegal! Your map files (ie map0.mul, statics.mul) are copyprotected by OSI. Thus you may not modify them. 
However completly replacing them is allowed. 

Connecting to an UOX server..... 
Here comes it  The T2A and all more recent versions have an additional paragraph in the installation license 
agreement, (which you had to accept to continue) saying something like that you will not provide or use any 
means other than OSI through which UO can played. Meaning if you connect to an UOX server you are invalidating 
your client license. owever with this issue they can only catch the fishes they want to keep, THEIR PAYING USERS! 
If you have an older client (pre T2A) this paragraph doesn't apply to you. Technically OSI could easily track 
people who connected to UO emulators, as the client does keep logs... However they only would scare away their 
paying clients, as most UOX players still pay each month for their OSI account. Unfortunally I'm didn't manage 
to find out what consquences a violation of an installation license could have. (other than invalidating this license). 
(( I would just would love to see what happens if someone brings back his UO package to his distrebutor with the words 
"I want my money back, since I didn't accept this license add-on"  he can throw the package away after that, 
since you have already seen the login serial-ID)) 

Providing older client.exe's for your shard 
is illegal!!!! This one clearly hurts OSI copyrights, even any disclamer for only experimental purposes or any 
other disclamer thus not justify/save you from this. Thus if someone once again has patched to fast (and not 
backuping his old client.exe) he is on himself, or until he finds someone else who is willing to violate this. 

To summerize it up. Some things are little in the gray zone. 

Even if some professional group would provide a hypothetical network with super-servers and that stuff, 
snagging away a real dangerous part of the OSI user base, a possible courtyard would be still very interesting, 
and I believe even law-experts couldn't predict the sentence for sure. 

After all we're just a small group, having our fun in UO in a little other way. On the other hand we provide 
free advertisment for OSI.... 

There is a major difference what OSI _can_ do, and what they _will_ do. Most of the actions they could do legally 
and technically are no justification for the money they will swallow. (beside the bad repitation that would grow) 

They are not likely to ban paying people for playing beside their OSI account on an UOX server. (why should they?) 
However they will ban people, if they get grib of the fact you logged in to an OSI server with modified static files, 
this is considered as cheating! 

You _do_ have to buy a client to be able to play on an UOX shard. 
You donnot have to have an account at OSI. (however it doesn't hurt either ) 

Knox