The latest release of libsmi is 0.4.8 .
Libsmi is freely available as a source code tarball for download at
http://www.ibr.cs.tu-bs.de/projects/libsmi/download/
The sources have once been managed using Subversion. In January 2021 the code was moved to a public GitLab repository (without any updates):
Libsmi compiles on most UNIX style platforms. Development primarily takes place on the Debian Linux platform. At least FreeBSD and W32-cygwin are reported to work also. You need a C compiler that supports long long types, e.g. gcc, and some tools that are present on most development machines (make, sed). Libsmi comes with a GNU autoconf configure script and libtool support to build static and shared libraries on many systems. For a complete build from scratch, you need GNU flex and bison (other lex/yacc implementation do not work), though generated scanner and parser C files are also included.
Libsmi has been packaged for some Linux distributions, e.g., Debian, RedHat, Mandrake, and SuSE. You may prefer to look for packages supplied by your favorite software package supplier, before you compile libsmi from scratch.