Minimize on close behavior made optional.
See the Changelog for list of features and fixes currently only available in the nightly builds.
Thank you for broaching the subject :) I intend to add a small 'Support Soulseek!' at the top right corner of the client window at some point. This will take you to a web page that allows you to make a donation, and once your privileges are activated, the button will display your remaining days of privileges left instead.