To further echo tirwhan's response, I've been paid to write custom versions of modules I've released to CPAN. I've also been paid to expedite enhancements to modules I've released to CPAN. OSS doesn't mean free as in beer - it means free as in speech.
Another way to look at it is RedHat - how on earth do they make their money? :-)
My criteria for good software:
Does it work?
Can someone else come in, make a change, and be reasonably certain no bugs were introduced?