The first GPL design for an asterisk-compatible analog card was published a week or two back by the ucAsterisk project. It's a four-port FXO design. I haven't been blogging so I missed reporting this. It's still in a design review stage, so it hasn't been tested yet. If you are so inclined, check it out and provide some input!
This is a good stage at which to get involved with a good project. The design link above actually includes a design review checklist and helpful links for reviewing the design with open source EDA tools.
Update: In the time it took me to post this, the ucAsterisk project had put out GPL designs for primary rate hardware as well. Looks like the CTI hardware front is pretty well GPL'd. </announcement>