Whenever I meet a director or CEO of a software company and talk to them about FSF and talk them into considering licensing their software with GPL, at first they listed but then the fear factor takes over.
1. Don't worry too much about what they think. While their help is welcome, we must never feel we desperately need it.
2. Show them the example of TrollTech and MySQL.
3. Say, "If your competitor distributes a version of this, you will be able to use his improvements."
Don't expect to convince them all, or even the majority.