The Wuffs project is both a programming language and a standard library written in that programming language (and then e.g. transpiled to C). For more details on the former, see the Wuffs the Language document. As for Wuffs the Library (also known as “std”):
/std./doc/std./example. A simple way to get started is to run the build-example.sh script in the top level directory./test./fuzz.It is perfectly feasible to use Wuffs the Library as a C library, without depending on Wuffs the Language tools (such as its compiler). Although the standard library‘s source code is in Wuffs the Language, the transpiled form is also checked into the repository. Using the standard library’s C form would be like using any other third party C library. It's just not hand-written C.
To do so, you need to download only one file, from the /release/c directory. Wuffs the Library's C form ships as a single file C library, targeting the C99 standard. That file acts as either a traditional .c or .h file depending on the presence or absence of a WUFFS_IMPLEMENTATION macro definition.
Most of the example programs treat it as a .c file. The /example/toy-genlib program treats it as a .h file, and requires a separate step (running wuffs genlib beforehand) to build the library implementation (a libwuffs.a or libwuffs.so file).