The licence file looks like html, not txt (https://github.com/Cracert/GIS-icons/blob/master/LICENSE.TXT)

Ouch, fixed.

Do we need to copy the license file in the built software?

The license statement is "I only ask you to let me know about that and to include licence.txt file in your work."

So, sounds like "to be included" - however, @Cracert may decide.

Small typo

It's written that way in the repo, in the file we need to include. Maybe make that suggestion in his repo?

Per @Cracert response by mail, it is not needed to have the license text file copied on installation:

Hello Robert,
We have a question regarding how to respect your licensing wishes here, would you mind jumping in to clarify if the license text must simply be in the source code, or must be copied over on each end user’s installation as well?

Hello Edouard,

There is no reason to spam users with such files, so please choose a simpler solution.
Thanks guys for your work!

Kind regards,
Robert Szczepnek