It it happening because Package Control, is overriding this version with the other one.
I opened a pull request to renaming the package control version:
#7193 Renamed Amxmodx package to AmxxEditor
But it will take a while before they merge, you can add the `amxmodx` package to the Package Control `auto_upgrade_ignore` setting. Then, Package Control will stop overriding it.
To do it, you can go to the Sublime Text menu `Preferences -> Package Settings -> Package Control -> Settings - User` and create a new setting entry with:
Code:
"auto_upgrade_ignore":
[
"Amxmodx",
],
Now, you can delete the `Amxmodx` package and reinstall it, i.e., delete the folder `Packages/amxmodx` and unpack the one available on the first post.