This project is kinda old but I want to give it a mention since the remastered Command & Conquer is coming out in a few weeks.

https://springrts.com/

I'm on Linux, trying to build Spring from source and I'm not having much luck. They've got a link to a Steam version of Zero-K which should be easier to install (naturally, no cost)

I find it funny how there's a free RTS engine with source code available, yet Steam charges $35 for Age Of Mythology, which is very very old. I wish someone would do a fundraiser for Spring to get better support, including Linux installers and solutions to common build issues that I'm experiencing.

edit: just had a thought - why doesn't someone bring this game to GOG? Get a Zero-K installer going. I have no idea how to do it, of course :P

The frame rate is choppy but I played a few missions of Zero-K

video: https://youtu.be/tyrlmlL2MkY

I recall reading and being intrigued by some "free RTS game engine" project already like 10 years ago. Maybe it was this one then, not sure if there are others. The engine is one thing. Creating a full game with a meaningful single-player campaign, voice actors, story, etc., that's another. Bring what game to GOG? Some freeware game based on that free RTS engine?

Not sure how much business sense it would make GOG to host games that can be (legally) downloaded for free from elsewhere on the net. If GOG tried to charge any money for them, then they'd have to agree with all the authors who had made maps for the game based on that engine, not sure if they'd have to agree even with everyone who has contributed to the development of the engine itself, etc.

Not as straightforward as it might seem at first.

The engine looks good. Wish I had time to tinker with it!

But...

Love what I just watched of one of the games -- Spring 1944! Wow! Just wish it wasn't an MP-only RTS.

timppu: steam has Zero-K in their store and it's free. If GOG did the same then I could promote a GOG version.

Yeah, I remember to hear about this. Though I'm not sure if it's still relevant as Unreal Engine now also free and can be used for all sorts of games, including RTS.