Maybe drop by the Discord to see if anyone can help you debug the issues you've run into.
Also, just because it might be hard to use on non-closed systems doesn't make something not open source.
If so, that is a serious impediment, tbf.
Unfortunately non-open source artwork is a problem with many games whose sources were released by the original publishers, after they abandoned any commercial plans.
For example I'm a big fan of OpenRA, but its artwork is still non-free.
I think ZeroK is a great game, and BAR probably also, so I didn't mean to distract from the great accomplishments of its FLOSS gameengine authors.
It's somewhat easier for BAR despite in theory being harder due to the lack of these standalone files due to the rapid file system, but in practice easier because you can just use the unofficial Skylobby (BAR still uses Springlobby protocol, at least for now).
Another Total Anhilation clone is unfortunately also not completely open source: ZeroK Unfortunately it is difficult to play ZeroK without steam and near impossible to setup a local LAN game with ZeroK.
Edited, because I recognized to late, that Wikipedia mentions that zeroK-Artwork might also be under CC-by-NC-ND.