This weekend, I attended an international meeting of the Free Pascal Development team, hosted by Marco van de Voort in Eindhoven, which happens to be just a few miles from my home. This was an informal meeting with barbecue et al (and Marco trying hard to set his house and garden on fire).
A topic that I should mention here, is the many units that FPC has to interface with external packages. For many packages, there are no GPC alternatives being actively maintained. For Mac OS X however, a common set of Pascal interfaces to system software is maintained by a small team, from which interfaces are auto-generated for GPC, FPC and MW Pascal. So, in general, I think working together with the FPC team is a good idea (and for Mac OS X, we already do so actively).
Anyway, the FPC team accepts {$ifdef __GPC__} patches to their interfaces and are open to discussions on other solutions. I don't have much time now to look into this, but this may change in say two or three months. Of course, volunteers are welcome.
Regards,
Adriaan van Os