termlib.js license is problematic

[dreamlayers]

termlib.js claims to be "free" but actually has some restrictions. Here is its license found in emscripten/termlib.js in this repository:

  This JavaScript-library is free.
  Include a visible backlink to <http://www.masswerk.at/termlib/> in the
  embedding web page or application.
  The library should always be accompanied by the 'readme.txt' and the
  sample HTML-documents.

The version here is v1.63. At http://www.masswerk.at/termlib/ the same license appears. The version available there is v1.66 and contains the same license. According to the version history v1.5 changed the license. It wasn't better before though. This is an old license from v1.42:

This JavaScript-library is free for private and academic use.
Please include a readable copyright statement and a backlink to <http://www.masswerk.at>
in the web page. The library should always be accompanied by the 'readme.txt' and the
sample HTML-documents.

The term "private use" includes any personal or non-commercial use, which is not related
to commercial activites, but excludes intranet, extranet and/or public net applications
that are related to any kind of commercial or profit oriented activity.

For commercial use see <http://www.masswerk.at> for contact information.

Any changes to the library should be commented and be documented in the readme-file.
Any changes must be reflected in the `Terminal.version' string as
"Version.Subversion (compatibility)".

So, this project may be violating the v1.63 license by not distributing "'readme.txt' and the sample HTML-documents." as part of this repository. Also, while building the PDCurses demos and viewing them locally ought to be okay, putting the results up on a web page would violate the license due to lack of "a visible backlink to http://www.masswerk.at/termlib/". These things wouldn't be hard to take care of. Termlib.js and associated files could go into emscripten/termlib, the HTML could be altered to add the link, and this licensing could be documented in README.md.

The biggest problem is that this seems to be incompatible with the GPL. The need for the backlink is similar to the BSD advertising clause, which the FSF has explicitly stated is incompatible with the GPL. So, for example, you couldn't use this library from DOSBox.

I can happily ignore this problem when playing with stuff, but I wouldn't like to distribute things that violate licenses, and it's a serious issue if this is to be used for porting various curses software to Emscripten.