Check out Freeciv by the way, a libre civilization clone. It's my personal favourite. As for games that aren't clones, there's an Android game called Doors of Doom. I've been thinking about making a game inspired from it for Linux, both mobile and desktop, but I'm not sure how I feel about it yet.
I'd love to see your reviews!
Songs of The Eons, 3.0 has become libre and open-source, it's still pre-alpha but it's developing pretty fast for a small Dev team
Try it out
From a quick search, looks good although definitely not close to completion, I'll add it to my list.
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!
Well, there's the odd hybrid that is OpenTyrian. The code is GPL2 and the assets are separately available as freeware (ie. gratis but not free-as-in-speech). That puts it in the same boat as e.g. OpenXcom (free engine, nonfree assets) but makes it slightly cheaper.
Tyrian is a bit unique as a shmup; you don't immediately die when you get hit and you get to customize your ship. Development of the open source engine has been extremely slow (the last release is two years old) but then again the project just aims to be a modern implementation of one specific MS-DOS game and it does that job just fine.
Tyrian is great fun, and open tyrian works fine. I recommend them.
Endless sky is really fun, and might scratch the same minmax itch as thrive.
Endless Sky is a 2D space trading and combat game similar to the classic Escape Velocity series. Explore other star systems. Earn money by trading, carrying passengers, or completing missions. Use your earnings to buy a better ship or to upgrade the weapons and engines on your current one. Blow up pirates. Take sides in a civil war. Or leave human space behind and hope to find friendly aliens whose culture is more civilized than your own.
One of my favourite games out there - not just open source ones specifically, but like all games included.
There's HyperRogue, a very fun and interesting game both on PC or mobile
Yeah I've actually played that before, never played to completion mind you, I ought to get round to finishing it sometime.