Here is simple way to get the categories in Mura
<cfscript>
variables.stInputs.siteid='#variables.$.event('siteid')#';
variables.stInputs.parentID='';
variables.gateway = variables.$.getBean('categoryGateway');
variables.qGetCategories = variables.gateway.getCategories(argumentCollection=variables.stInputs);
writeDump(variables.qGetCategories);
</cfscript>
Return type is query and we can add this code snippet in Mura template