How to access the server without using the left-wing programs?
That is to go directly through сlient.eхe
How to hack? or patch?
You have to use a hex editor to modify the client.exe in any way. Its not recommended for the feint of heart though, and also not recommended legally by EA/Mythic.
010 Editor is the one I've used in the past, but not for editing anything from EA/Mythic. o_O

Note: please don't post any sort of modified client.exe or any other such proprietary file here on the boards, or we'll have to delete it - not saying you will or would, but just in case.
You did not understand me! I suspect that the case in the server (as configured) that would be on the server 54 could just go through client.exe
I still don't think I'm understanding you. Are you asking how to edit the ServUO.exe? If so, you just edit the files contained within the "server" folder provided on the Git page (using Notepad++, Visual Studio, SharpeDevelop, etc), and simply recompile it into a new ServUO.exe.

If that also isn't what you're asking, then you may have rephrase the question or use a different translation software.
I think he is asking is the server can handle the decryption of the client. The answer is no, you have to use a third party (like UoSteam or Razor) or a client that is decrypted.
At the moment the game can come only through the Razor. I ask how to configure that you could go to the game through a simple client client.exe
You have to edit the client as m309 said, using a hex editor to remove the encryption of the client.exe, which would be illegal and will not be described here.
Fingers jumped in before I had time to reply (Sorry work was intense yesterday). Yes, you can use the link Fingers posted to decrypt the client without need of using Razor or UOSteam. You just have to modify your login.cfg.