The Apache Vysper developers communicates using our Mailing Lists. If you have any questions, feedback or suggestions, you're very welcome to join the list and send an email. We are also happy to receive bug reports and feature requests in our JIRA.
The best chance of getting your bug or feature fixed is to provide a patch, if they fit our goals we will usually have them commited within a few days. The Apache Contributors page has excellent information on how to produce patches.