I am curious about how do you protect your software against cracking, hacking etc.
Do you employ some kind of serial number check? Hardware keys?
Do you use any third-party solutions?
How do you go about solving licensing issues? (e.g. managing floating licenses)
EDIT: I'm not talking any open source, but strictly commercial software distribution...
Almost all copy-protection is both ineffective, and a usability nightmare. Some of it, such as putting root-kits on your customers' machines becomes downright unethical