You should use "setvar" rather than "command" to set variables.
(setvar "secureload" 0)
You might also want to leave "secureload" on because its a layer of protection. I think a better approach would be to add your *.lsp path to the trusted paths instead. Also it is a good habit to check if a file is present before trying to use it. The same goes for variables. Don't just blindly add another instance of the trusted path. Check if it is already added before that.
;Check if ACAD version is 2014 or newer
(if (>= (getvar "ACADVER") "19.1")
;Check if the path "M:\\DESIGN\\C3D\\MWU C3D Files\\AutoLisp\\" is part of the trusted paths
;If it is not, then add it to the trusted paths
(if (not (wcmatch (getvar "trustedpaths") "*M:\\DESIGN\\C3D\\MWU C3D Files\\AutoLisp\\*"))
(setvar "trustedpaths" (strcat (getvar "trustedpaths") ";M:\\DESIGN\\C3D\\MWU C3D Files\\AutoLisp\\;"))
);if path
);if acadver
;Check if the file "MWU.lsp" exists
;If it does, then load it
(if (findfile "M:\\DESIGN\\C3D\\MWU C3D Files\\AutoLisp\\MWU.lsp")
(load "M:\\DESIGN\\C3D\\MWU C3D Files\\AutoLisp\\MWU.lsp")
);if findfile
Make sure you dont leave global variables too. Either define a function, localize the variables there and execute it, or set them to "nil".
;Set a list with all the variables
(setq *varlist* '(companyEnterpriseCUI companyCustomDictionary companyPC3 companyPMP))
;Clear all the variables
(foreach x *varlist* (set x nil))
;Clear the list
(setq *varlist* nil)
