The runtime is the part of the GF system that implements parsing and linearization of texts based on a PGF grammar that has been produced by the GF compiler.
The standard GF runtime is written in Haskell like the rest of the system. Unfortunately this results in a large memory footprint and possibly also portability problems, which preclude its use in certain applications.
The goal of the current task is to reimplement the GF runtime as a pure C library. This C library can then hopefully be used in some situations where the Haskell-based runtime would be unwieldy.
Preview versions of the implementation, libpgf, are available from the project home page. This is also where up-to-date documentation can be found.