It depends.
The compatibility between ISC License and GNU Lesser GPL v2.1 depends on the specific clauses and the way the two are combined in your project. Have a qualified lawyer review before redistributing.
| License | Family | Patent grant |
|---|---|---|
| ISC License (ISC) | permissive | No (implicit at most) |
| GNU Lesser GPL v2.1 (LGPL-2.1) | weak-copyleft | No (implicit at most) |
ISC License: Functionally equivalent to MIT; Internet Systems Consortium's house license.
GNU Lesser GPL v2.1: Library copyleft: dynamic linking permitted from non-LGPL code without triggering full copyleft.
If you found this page because you're trying to figure out whether shipping a particular dependency is safe, the answer above is a starting point — not a substitute for reading the actual licenses or talking to a lawyer when stakes are high.
LicenseHound walks every transitive dependency in your repo, maps each to its SPDX license, and flags pairs like this one in PR comments. The CLI is free; the team dashboard is paid.