Several times the gnuplot-license was discussed wrt/ compatibility with free, open-source licences. Obviously the general opinion is that the gnuplot-license is not GPL-compatible and not exactly DFSG-compatible. But that's not my point here.
In bitmap.c is says:
   ** You may use this code for anything you like as long as
   ** you are not selling it and the credit is given and
   ** this message retained.
This seems to prohibit any use of gnuplot in a commercial environment.
Do I get that right?
If yes, I propose to present this fast more prominently in the documentation
and the website. Are there any chances that the respective code is removed
at some point in the future?

I'd like to hear the projects'  stance on this issue.

Greetings,
Stefan Schroeder

Actually that should be
… present this _fact_ more …

Good catch.
The text you quote is not from the general gnuplot copyright notice;  it is attached only to the set of raster operations in the file you quote, bitmap.c.    To the best of my knowledge, these routines are used only by drivers for the 1980s/1990s generation of printers:
        hp500c.trm hpljii.trm hppj.trm pbm.trm epson.trm
In a quick test I de-selected those terminals from the default build configuration and was able to link without including bitmap.o

It is not hard to do this manually if you need to build an executable for which that restriction does not apply. It would also be easy to make it a configuration option,   ./configure -without-bitmap-terminals   or something of the sort.

Of course if you really do need support for hplj-era printers, it would remain a problem.

Other suggestions?

Here you go.  This patch adds a configuration option  ./configure -without-bitmap-terminals
    https://sourceforge.net/tracker/?func=detail&aid=3101992&group_id=2055&atid=302055

It applies to both current 4.4 and current 4.5 source trees.

Wow, thank you Ethan, for the quick and thorough reply! You're my hero for today (and some days coming) :-)

Hi,
Looks like the routines in bitmap.c are needed for linux-vga too:
https://sourceforge.net/tracker/?func=detail&aid=3481336&group_id=2055&atid=102055
https://bugs.gentoo.org/show_bug.cgi?id=401191

Has anyone tried to contact the author and its former company? Maybe they would be willing to relicense it?
The code in question was posted in 1987 as a patch for gnuplot 1.1 to net.sources:
https://groups.google.com/group/net.sources/msg/df5ff7e393f34671

The author Jyrki Yli-Nokari seems to be at Nokia now: <jyrki.yli-nokari@nokia.com> and Intrinsic Ltd. is this company in Finland: http://www.intrinsic.fi/en/

Regards,
Ulrich

It looks like the vga/svga don't really need the raster operations. They just use the 5x9 bitmap font, which may well have originated from a non-encumbered source (but I certainly don't know exactly where it came from). Perhaps they could be switched to use one of the bitmap fonts from another terminal?

Catched this thread googling myself. I am the author of the original bitmap routines. The copyright note is really old and I'll be happy to remove the restriction to distribute and provide the original code under the general gnuplot license so no need to patch the code. Let me know how