If you are going to render a template with a helper, you either need to tell Meteor not to escape the string. If it's escaped, Spark won't render it. This is a useful default feature that prevents arbitrary code from being injected into your site, and generally makes it clear what's being rendered.
To do this, you can either write it in triple brackets in the template
<template name="body">
{{{include "myTemplate" attr=value}}}
</template>
or return a SafeString
in the helper
Handlebars.registerHelper('include', function(templateName, options) {
return new Handlebars.SafeString(Template[templateName]({name: 'stackoverflow'}));
});
On a related note, the Meteor handlebars documentation notes that a few helper names are reserved. It doesn't appear that include
is one of them, but you should be careful using names that sound like keywords.