The latest version of umlgraph on Mavencentral appears to be 5.6.6:
https://mvnrepository.com/artifact/org.umlgraph/umlgraph
It would be good to have the latest version available as a managed dependency via maven, jcenter, etc.
As workaround, I am currently considering to use the auto-compiled version from https://jitpack.io/#dspinellis/UMLGraph - a pretty interesting idea, to have a service that can automatically build jars for github software. But I'd rather have a signed version in a repository like maven.