From the post:
Ontopia’s developer team is committed to switch from Ant to Maven as build and project management tool for the Ontopia code base. Making this switch has been ongoing work since 2009. This blog post serves as a summary of the work that has been done so far and the work that still needs to be done.
Near the end of the post, you will find:
You can help us by building Ontopia with Maven yourself and either trying out the distribution or the new artifacts as dependencies in other projects. Issues you find can be reported on the Ontopia issue tracker. Keep in mind however that this branch is quite old and might not contain fixes already committed to the trunk.
So, you can have topic map software while learning or practicing your skill with Maven.
Sounds like a win-win situation to me.