#596 Inquiry regarding potential license modernization (GPL compatibility)

[josh allen]

Dear gnuplot development team,

First, thank you for maintaining one of the most reliable and powerful plotting tools in the ecosystem. I am writing to respectfully ask if the team has recently revisited the possibility of dual-licensing gnuplot under a GPL-compatible license (such as the BSD 3-Clause or the GPL itself).

While the current license has served the project for decades, it creates friction for modern distribution workflows and integration with other FOSS toolchains.

I understand that the copyright history of gnuplot is extensive, making a license change legally complex. However, has there been any discussion regarding a "Contributor License Agreement" for new code, or a long-term plan to transition the license as old components are refactored?

Best regards, Josh

[Ethan Merritt]

Several years back Daniel Sebald made a concerted effort to contact gnuplot developers, past and present, to ask about their license preferences. The consensus did not favor any attempt to relicense existing code under the GPL, although note that several major components (Qt and cairo terminal drivers) were contributed with GPL as an alternative license. When new gnuplot features are implemented in a separate source file, rather than solely as modifications to older source files, I have encouraged the author to dual-license using a 2- or 3- clause BSD license.

There were at one time some gnuplot components, notably the original pdf terminal, that depended on a library limited to "non-commercial use" without a separate license. These components were removed (e.g. the pdf support moved to the cairo and Qt terminal code, both of which are explicitly GPL-compatible).

I am aware that some people who build and distribute gnuplot binaries have chosen to be conservative in their choice of configuration options in order to avoid linkage to certain shared libraries, notably gnu libreadline. I personally believe these concerns to be unwarranted, but I am not offering legal advice and (at least in the case of readline) gnuplot already offers an alternative configuration option to link a BSD readline library instead.

Does that answer your question?

I haven't tried to list or summarize every issue that I recall has been raised with regard to copyright or license terms since I joined the project. If you have a particular concern in mind, feel free to follow up here or post a query to the gnuplot-beta mailing list for developers.

[josh allen]

Yes thank you after I heard about php moving to 3 clause bsd I use gnu plot
in qualculate and it calls on gnu plot instead of doing it internally

On Mon, Apr 27, 2026, 3:32 PM Ethan Merritt sfeam@users.sourceforge.net
wrote:

Several years back Daniel Sebald made a concerted effort to contact
gnuplot developers, past and present, to ask about their license
preferences. The consensus did not favor any attempt to relicense existing
code under the GPL, although note that several major components (Qt and
cairo terminal drivers) were contributed with GPL as an alternative
license. When new gnuplot features are implemented in a separate source
file, rather than solely as modifications to older source files, I have
encouraged the author to dual-license using a 2- or 3- clause BSD license.

There were at one time some gnuplot components, notably the original pdf
terminal, that depended on a library limited to "non-commercial use"
without a separate license. These components were removed (e.g. the pdf
support moved to the cairo and Qt terminal code, both of which are
explicitly GPL-compatible).

I am aware that some people who build and distribute gnuplot binaries have
chosen to be conservative in their choice of configuration options in order
to avoid linkage to certain shared libraries, notably gnu libreadline. I
personally believe these concerns to be unwarranted, but I am not offering
legal advice and (at least in the case of readline) gnuplot already offers
an alternative configuration option to link a BSD readline library instead.

Does that answer your question?

I haven't tried to list or summarize every issue that I recall has been
raised with regard to copyright or license terms since I joined the
project. If you have a particular concern in mind, feel free to follow up
here or post a query to the gnuplot-beta mailing list for developers.

---

[feature-requests:#596]
https://sourceforge.net/p/gnuplot/feature-requests/596/ Inquiry regarding
potential license modernization (GPL compatibility)

Status: open
Group:
Created: Mon Apr 27, 2026 04:22 PM UTC by josh allen
Last Updated: Mon Apr 27, 2026 04:22 PM UTC
Owner: nobody

Dear gnuplot development team,

First, thank you for maintaining one of the most reliable and powerful
plotting tools in the ecosystem. I am writing to respectfully ask if the
team has recently revisited the possibility of dual-licensing gnuplot under
a GPL-compatible license (such as the BSD 3-Clause or the GPL itself).

While the current license has served the project for decades, it creates
friction for modern distribution workflows and integration with other FOSS
toolchains.

I understand that the copyright history of gnuplot is extensive, making a
license change legally complex. However, has there been any discussion
regarding a "Contributor License Agreement" for new code, or a long-term
plan to transition the license as old components are refactored?

Best regards, Josh

Sent from sourceforge.net because you indicated interest in
https://sourceforge.net/p/gnuplot/feature-requests/596/

To unsubscribe from further messages, please visit
https://sourceforge.net/auth/subscriptions/