Yes, Github changed this in April, 2013:
We added the X-Content-Type-Options: nosniff header to our raw URL responses way back in 2011 as a first step in combating hotlinking. This has the effect of forcing the browser to treat content in accordance with the Content-Type header. That means that when we set Content-Type: text/plain for raw views of files, the browser will refuse to treat that file as JavaScript or CSS.
But thanks to http://combinatronics.com/ we can include GH scripts. The only change is from raw.github.com that becomes combinatronics.com:
<script
type="text/javascript"
src="https://combinatronics.com/username/repo/master/src/file.js"
></script>
The project is hosted on Github being open-source.
And yes, @Lix is correct. The files are not being served from Github but from combinatronics.
Another workaround I found is that instead of:
<script
type="text/javascript"
src="https://combinatronics.com/username/repo/master/src/file.js"
></script>
you can use $.getScript jQuery function:
<script>
$.getScript("https://combinatronics.com/username/repo/master/src/file.js", function () {
/* do something when loaded */
});
</script>