> However it is not clear to me how this source code can be used by fpc.
> I added the zeos path to the fpc.cfg file, but I get a number of
> compilation error.
> For instance
> Fatal: Can't open include file "../Zeos.inc"
> With Lazarus I would build a package and all zeos components would be
> immediately available for my programs.
Open the package->Options->Show Options, that's the list of compiler options you must pass when building the package without Lazarus by compiling the registration unit (the one has the same name as the .lpk, but with .pas / .pp extension). The unit itself might not be useful without Lazarus, but it helps building the whole package as it has all the units as dependency. When done, add -Fu to the package's compiled units directory when compiling your program.
> What happens when only FPC is at hand ?
You can no longer close your eyes to what happens under the hood behind Lazarus -> FPC communication.
> Is FPC the child of a Lesser God ? :)
Quite the contrary, FPC can live by itself, Lazarus is dead without it.