- could you lighten me about the instructions you have writed ?

are keycode 63 and keycode 66 the alt and apple keys ?

- what are the numbers of ctrl key, shift key... i mean if i want to

customize this

Maybe a small tool like 'xev' can answer these questions.  Just start it, move the mouse inside the opening window and press the key you are interested in.  'xev' will print all available data about the occurring X event.  The key code should be part of this event.

A larger tool like 'xkeycaps' might be available for MacOS as well.  It displays a keyboard with a choosable layout and can change lots of properties of this layout.  It also can show you all the key codes of course.

- does anyone know any mean to make this automatic at x11 opening ?

There are lots of ways to help you:
- Use a shell script to start TeXmacs which does the xmodmap call before starting TeXmacs.

- Put the xmodmap calls into your login script (depends on your shell, so 'echo $0' and then 'man bash' or 'man tcsh' or whatever your shell is -- I don't know Apple enough -- to find out what your login script is called).
- Put the xmodmap call into a system-wide start-up script for X.  Again, I don't really know where Apple-systems store these.

Greetings,

Alfe