I think you can import locally downloaded files from CDN.
Or you can import from html and inside html
<link rel="stylesheet" href="https://unpkg.com/@atlassian/aui@9.3.0/dist/aui/aui-prototyping.css" media="all">
<script src="https://unpkg.com/@atlassian/aui@9.3.0/dist/aui/aui-css-deprecations.js"></script>
<script src="https://unpkg.com/@atlassian/aui@9.3.0/dist/aui/aui-prototyping.js"></script>
These styles with js I am using in my spring project inside template language. (like Handlebars for js)