Hi Nick,
Uniface supplies a version of Tomcat to offer an out of the box development experience, but Uniface can run on any webserver supporting the JAVA Servlet API version 2.3 or 3.0 - Uniface Web Application Server.
There was an article published a little while ago explaining how to update your Tomcat version which maybe of use - Apache/Tomcat 8 Uniface Migration Guide.
Uniface 10.4 will be delivered with an updated version of Tomcat.
Kind regards,
Mike