To get less to work on the server side with Orchard features you'll need to a do a few things:
1) You need to get DotLess to translate your less files into css, you can do this with a web config in your Styles folder. This also changes the result mime type to text/css so IIS will serve them. (you'll also need dotless.core.dll to be present in Orchards
<?xml version="1.0" encoding="UTF-8"?>
<section name="dotless" type="dotless.Core.configuration.DotlessConfigurationSectionHandler, dotless.Core" />
<dotless minifyCss="true" cache="false" />
<add key="webpages:Enabled" value="false" />
<!-- iis6 - for any request in this location, return via managed static file handler -->
iis7 - for any request to a file exists on disk, return it via native http module.
accessPolicy 'Script' is to allow for a managed 404 page.
2) Second you'll need to override the StylesheetBindingStrategy (which is a kind of IShapeTableProvider) and replace it with one that won't ignore an include or require with a .less extension, because the default one only creates shapes (Yes Orchard renders
stylesheet link tags with shapes) for files it can find with .css extensions. The one I am working with now is a hack (I won't lie), it simply re-performs the css shape building step
except looking for .less files. It does this AFTER the css files so any include or require that has a .less and .css version (I am talking to you Web Workbench Users) gets the .less version.
I am actually prepping a DotLess module for the Gallery, look for that in the coming days...