As per https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libassuan.git;a=blob;f=README;h=7ec27d3f62998df089eb3cb21ef9c46b9da3dc04;hb=HEAD the software is LGPLv2.1+ and the documentation is GPLv3+ Reproducible: Always
Also /usr/bin/libassuan-config is FSFULLR as stated in the header of the file