They are similar but different. BAR is more of a unique game (for better or worse), while ZeroK is much closer to an HD remake of Total Annihilation.
BAR used to stand for "Balanced Annihilation Reloaded" - so it's sticking very close to TA, while Zero-K has been experimenting much more freely with what is possible in the Spring/Recoil engine.
It's also probably a factor that BAR has spent a decade in development hell (under a different team than now ?), so it just didn't have the velocity to fork away sufficiently, even if it wanted to.
The first indicator of that popped up, when valve ended greenlight, and just greenlit all the things. Which propped Evolution RTS upon the steam front page for half a day, flooding the original lobby system and showing how inadequat the whole ecosystem was for that. The original Evo dev Forb learned from the whole mess after he returned from his day job.
Zero-k then learned the lessons, developed a ingui lobby, started the whole matchmaking and better server deployment, detached from the whole "one central server" thing of the spring eco system.
BAR did some graphical overhaul, with Floris, Beherith, Sprung and the whole original crew supported by new faces like Teifion and on and on. They optimized the Spring engine into a new version- more tailored to BARs needs and reworked alot of the stuff.
Its gpl open source, so the project order and who invented what is pretty flowy.. everybody copies from everybody, one progress is everyones progress..
I disagreed about «BAR is more of a unique game (for better or worse), while ZeroK is much closer to an HD remake of Total Annihilation.»
P.S.: You might also be mistaken about EvoRTS' Steam release being specifically behind the motivation of Zero-K splitting up, since according to lead ZK dev the second at least partially predates the first ?
http://zero-k.info/Forum/Post/236480#236480
> 2012(ish): Zero-K splits off to its own infrastructure after disagreement with infrastructure developers. From my perspective they were very stubborn regarding extending the protocol to allow for new stuff (Eg matchmacking, more advanced planetwars) and would make sudden changes that broke our autohosts.
> 2013-2014: Evolution RTS is greenlit on Steam and released in 2014. I don't think Steam was on my radar at the time, but now it looked like a possibility. Looking back at the dates we actually put up a greenlight campaign five days after the Evolution RTS release.
(Lobby interface issues being another thing, but then IIRC EvoRTS had already tried to improve on this before release, though not successfully enough ?)
BAR units are generally similar to TA units. It captures the feel of "what TA would be if it was full 3D and high resolution". Of course, balance is different, but TA balance was very odd.
ZeroK seems to have terrain modification mechanics which is not present in TA.
In BAR terrain can be damaged by big explosions, but it's very limited.
FWIW I never played ZeroK but based on their intro video BAR seems to be closer to TA visually.