Licenses

The bulk of Yosys is ISC. Some parts are public domain (kernel/hashlib.h, libs/sha1/, libs/bigint/). libs/minisat/ is under MIT (which is permissive and compatible with ISC).

ABC is a stand-alone binary with it's own set of licenses. At least in Debian ABC is its own package.

No part of Yosys is GPLv2, GPLv3, or LGPLv2. Some of the test cases are (because they are copied from designs that are using those licenses), but this should have no effect on the license status of Yosys itself.