This is from Free Pascal Unix FAQ
Dynamic libraries

These operating systems do support shared libraries (also called dynamic link libraries), Free Pascal currently does not emit position independant code (PIC), as required for the creation of shared libraries.

Therefore, even though the linux compiler target permits creating shared libraries, the usage of that shared library may result in undefined behavior, especially if accessing global variables in the library. Creation of shared libraries is not recommended with the current version of the compiler.

Importing code from shared libraries does work as expected though, since it does not require usage of position independant code.
You have to wait for 2.2 version I suppose.