If you need to display UTF8 and antialiased fonts from HTML in your Motif application, you can use updated version of XmHTML.
It was dormant for 10 years, but since Motif is now UFT8 and XFT capable, we had to fix XmHTML in order to continue to use it.
License is LGPL so you can use it in your commercial projects.
Works on Linux and OS X.
Sourceforge site has the screenshots.