Licence
This page brings together the licence information for CERNIS PRO — regardless of whether the application displays it itself.
The licence of the work
The packages shipped for CERNIS PRO carry the licence declaration GPL-2.0-only — the GNU General Public License in version 2, without the option of later versions.
The copyright notice reads: © 2026 Karl Bach
The licence has been determined as GPL-2.0-only — the GNU General Public License in version 2, without the option of later versions.
Why GPL-2.0-only
The choice of licence follows no preference, but the way the software is built. One bundled component binds it:
- scapy, the library used for packet analysis, is fixed to GPL-2.0-only. GPL-2.0-only and GPLv3 are incompatible with one another.
Distribution under GPL-2.0-or-later is therefore ruled out. GPLv3 or a permissive licence would only come into question once this component has been replaced. A dual or commercial licensing model is ruled out.
The question of the licence is thus less a licensing decision than an architectural one.
Source code
The source code is available as an archive in the same download area as the packages — with size, date and checksum like any other file.
Bundled components
CERNIS PRO ships third-party components: Python packages, components of the user interface, system libraries and data sets. Their licence information is collected afresh with every build — separately for each target platform. It is not maintained by hand.
Binding for the choice of licence are the components with copyleft: scapy (GPL-2.0-only) and zeroconf (LGPL-2.1-or-later) are shipped with their full licence text, others are under the MPL-2.0. At no level do AGPL, EPL, CDDL or SSPL occur.
The complete listing accompanies every package:
| Package | Location |
|---|---|
| .deb | /usr/share/doc/cernis-pro/copyright as well as 3rd-party-licenses.txt.gz |
| .rpm | /usr/share/licenses/cernis-pro/LICENSE.dependencies as well as LICENSES |
| all | lizenzaufstellung.json and LICENSE in the program directory |
A list of these components will be provided at this point as soon as it can be generated from the listing of the respective package. A list maintained by hand would diverge from the actual set — which is why none appears here for the time being.
Attribution
The bundled country flags come from the flag-icons project and are under the MIT licence, © 2013 Panayiotis Lipiridis.
The remaining bundled data sets require no attribution: the geo database (CC0 1.0), the database of network operators (PDDL 1.0) and the factory list of encrypted name resolvers (CC0 1.0).
The manufacturer identifiers come from the public registry list of the IEEE, for which no copyright is asserted. CERNIS PRO uses this registry list exclusively, no IEEE standards documents.
Prerequisite programs
Some programs are required but not bundled. They come from the distribution or are installed by the user; their licence terms are a matter for their publishers.
nmap is invoked for the port scan and is usually installed through the package manager.
Npcap is required for packet capture on Windows. Npcap is not part of CERNIS PRO and is not bundled; the user obtains and installs it from the vendor. Npcap is under a licence of its own, which is not open source and limits the number of installations for free use. The vendor’s licence terms are to be examined before installation. This note concerns the Windows edition.
On Linux and macOS Npcap is not required — there the system library libpcap takes on this task.
How this information comes about
Three rules apply to all licence information:
- Precedence of the package file. What the package file itself states is authoritative.
- No substitute text. Where no copyright notice exists, that is disclosed instead of one being inserted. A visible gap is correct; a filled gap would be a false statement.
- Change nothing. Licence texts are not shortened, not rewrapped, not translated.
The information differs by platform. On Windows and macOS there is no mapping from file to package; the level of embedded system libraries is not collected there. That is a statement about what can be determined, not about the content.
Full licence text
The full licence text of the GNU General Public License, version 2:
Read the licence text Download the licence text (17,984 bytes)