There are only two client interfaces included in the base
PostgreSQL distribution:
libpq is included because it is the
primary C language interface, and because many other client interfaces
are built on top of it.
ecpg is included because it depends on the
server-side SQL grammar, and is therefore sensitive to changes in
PostgreSQL itself.
All other language interfaces are external projects and are distributed
separately. Table H-1 includes a list of
some of these projects. Note that some of these packages may not be
released under the same license as PostgreSQL. For more
information on each language interface, including licensing terms, refer to
its website and documentation.
Table H-1. Externally Maintained Client Interfaces