Is it OK for other project to use Pelles C headers?

[dimmed]

I'm talking about the legal issue. There is another C compiler project named Orange C:

https://github.com/LADSoft/OrangeC

They have imported the Windows API headers from an old version of Pelles C to replace their outdated one. You can still find the relevant commits and issues on their Github repository. The Orange C developer said this is OK according to the license of Pelles C, but it seems they have never contacted Mr. Pelle Orinius officially.

[TimoVJL]

From a that Orange C licence:

The windows header files are derived from Pelles C.  Pelles C is derived from LCC.
The licensing for Pelles C is that things derived from Pelles C cannot be used commerically.
LCC also doesn't want things to be used commerically, but it has an additional stipulation
that there has to be acknowledgement of use.  These header files remain under the Pelles C
and LCC licenses and are not covered by the GNU license that the rest of the runtime library
abides by.

[Robert]

https://www.smorgasbordet.com/pellesc/termsofuse.htm

Pelles C is freeware for any use: personal, commercial, etc. No registration is required to download it, and you can use it anonymously.
Pelles C can be freely distributed, but it can not be sold.
Pelles C is provided 'as-is', without any expressed or implied warranty. In no event will the author be held liable for any damages arising from the use of this software.

Pelles C is totally free. However, some users may want to express their gratitude by donating some money.
If Pelles C is a major part in building a product sold for money, it seems fair (to me) to donate a little bit of that money to Pelles C - but this is never required.

Donations will help to pay for this website, my time spent on support, and any possible new versions.