@YannFlare - I *think* you forgot the game is open-source.  The whole source code of the game is in two repos. See :-

https://github.com/clintbellanger/flare-engine
https://github.com/clintbellanger/flare-game

Just clone those two repos. You should be able to get where the items are shared.

I know that both fantasycore/items.txt and alphademo/items.txt have some of the items list you want. 

Then there is ItemManager, ItemStorage and Loot.cpp/h files which are in flare-engine/src/

You probably would find what you need in one of these files.

Disclosure :- I am not a coder/developer.

just to be straight, 'Tiled' is not freeware but free software. Here's the diff. Couple of links should give you a slightly better understanding :-

https://fsfe.org/freesoftware/basics/comparison

http://fossforce.com/2012/07/zonealarm-defining-difference-freeware-free...

At the very least, if you do put up the sources, I can try to build it in linux and play. Even if it doesn't build can put up tickets for the same.

Also having the sources do make more people try it as well. See for instance https://github.com/Bertram25/ValyriaTear and a nice little community which is there around it.

See https://github.com/clintbellanger/flare-game/ as well as a mod of the same  https://github.com/RyanDansie/flare-mod-noname

There are others such as polymorphable https://github.com/makrohn/polymorphable and erebus erebusrpg.sourceforge.net

All of the above are rpg's.

umm.... is your game open-source/foss or not ?

One another thing, you could have some sort of script which tracks that each art has some kind of license and attribution given to it. I have seen a few projects do like that which does lead in some instances more art created specifically for that project as well. So it's a win-win in any case.