I've been discovering that despite what I originally thought - there exists a small collection of high quality games which are not only free but also developed openly.
I'll list the ones I have found to date, I wouldn't mind seeing any recommendations!
Mindustry - Essentially a fully complete indie game. You can buy it on steam to gain access to a few other features but nothing game changing.
Super Tux Kart - Literally Mario Kart.
Super Tux - Literally Mario
Luanti formerly Minetest. - A voxel game engine, you can add hundreds of mods to make the game into what you want, including into just straight up Minecraft.
Veloren - An open MMO, still very much in alpha development
Thrive - Spore on steroids, still in development although I've spent a good 20 hours having a lot of fun with where it's at, at the moment - with the bacteria stage mostly complete and the multicellular stage taking shape.
Unciv - just civilization.
One thing you probably notice with this list is there are a lot of games which are clones or essentially clones of other games. So I wonder if anyone knows of games which have their own unique style and ideas?
I'll probably post some reviews of each of these games and any more I find out about in separate posts.
Here's a Wikipedia list, but if anyone has any favorites rather than me just dumping a list of varying quality games on to this post.
Not sure if Pixel Dungeon (and its derivatives) fit in this. They're released under GPLv3. But it's a complete game, and not a clone (though it follows the traditional roguelike genre).
In the same genre, check out Dungeon Crawl Stone Soup.
From the looks of it Pixel dungeon 100% fits the libreculture community, I'll it to my list to play and then review or you could write a review if you like - it would be cool if more people join me.
Ooh, there's also Shattered Pixel Dungeon, which I believe is a spin-off of the original. I could write a review, but I tried writing game reviews once before, and faced criticism for how poorly I had done it. Maybe I could consider trying again.
Go for it! My writing isn't amazing, I miss the endings of words frequently. But its all practice and practice + feedback makes perfect. You can't mess it up so badly that it's unfixable!