When you write a custom menu then load it, AutoCAD compiles it and writes two other files. .mnr and .mnc
These files are encripted whereas your .mns file remains readable. However, you can remove the .mns once AutoCAD has compiled it as all it needs is the .mnc file to work.
If you don't want anyone to see your code, just remove the .mns file from the support folder.
Try reading your .mnr and .mnc files with your text editor and you'll see your code is quite safe.