LicensedBundler

An add-on to the Microsoft ASP.NET Web Optimization Framework bundling and minification that preserves /*! Important Comments */ for licensing (or any other) purposes.

This also protects against changes in user-agent which can cause your production bundles to be returned with all comments and unminified, as covered in Changing User-Agent to Eureka/1 Changes Output in ASP.NET Bundling and Minification.

Implementation

Get the package from NuGet

Instead of using ScriptBundle or StyleBundle in your BundleConfig.cs, use LicensedScriptBundle or LicensedStyleBundle.

public static void RegisterBundles(BundleCollection bundles)
{
    bundles.Add(new LicensedScriptBundle("~/bundles/jqueryval").Include(
                  "~/Scripts/jquery.unobtrusive*",
                  "~/Scripts/jquery.validate*"));
                  
    bundles.Add(new LicensedStyleBundle("~/Content/css").Include(
                  "~/Content/site.css",
                  "~/Content/site2.css",
                  "~/Content/site3.css"));
}

So your css:

/*! 
    This will be visible in bundled and minified version.
    It's important!
*/

/* other comments you don't want people to see. */

html {
    background-color: #000;
    margin: 0;
    padding: 0;
}

body {
    background-color: #fff;
    border-top: solid 10px #000;
    color: #333;
    font-size: .85em;
    font-family: "Segoe UI", Verdana, Helvetica, Sans-Serif;
    margin: 0;
    padding: 0;
}

becomes this:

/*! 
    This will be visible in bundled and minified version.
    It's important!
*/
html{background-color:#000;margin:0;padding:0}body{background-color:#fff;border-top:solid 10px #000;color:#333;font-size:.85em;font-family:"Segoe UI",Verdana,Helvetica,Sans-Serif;margin:0;padding:0}

Same for JavaScript. So the default jQuery bundle goes from this:

!function(n,t){"object"==typeof module&&"object"==typeof module.exports?module.exports=n.document?t(n,!0):function(n){if(!n.document)throw new Error("jQuery requires a window with a document");...

To the more appropriate

/*! jQuery v2.1.0 | (c) 2005, 2014 jQuery Foundation, Inc. | jquery.org/license */
!function(n,t){"object"==typeof module&&"object"==typeof module.exports?module.exports=n.document?t(n,!0):function(n){if(!n.document)throw new Error("jQuery requires a window with a document");...