Reporting a Bugs
Reporting a bug concerning dar or libdar can be done by creating an issue at github. But before doing so, thanks to check an issue is not already open for the same problem, in which case you are welcome to add your comments to this already opened issue.
But in case of doubt, it would be appreciated to first ask for support on the dar-support mailing-list, you will probably get quicker an answer and this will benefit to others meeting the same problem.
Feature requests are listed here. You can vote for the one you want to be implemented (the ones that interest most people get implemented first) or add your own one.
Provide or use a patch
You are free to provide a patch for dar and/or libdar by mean of pull request on github.
General discussion about
The dar-discussion mailing-list is open for discussion about dar/libdar and other software relying on libdar when this is not related to support requests or bug report.
Contact the author/maintainer
However, just in case, you get email address from the gpg key used to sign the releases and also find it from the AUTHOR file present within the source code.