Another Total Anhilation clone is ZeroK which is unfortunately also not completely open source because of its artwork license (Wikipedia mentions CC by NC ND but I could only fjnd this summary https://github.com/ZeroK-RTS/Zero-K-Artwork/issues/16).
Unfortunately it is near impossible to setup a local LAN game with ZeroK, since there are no current instructions to setup the required spring-engine lobby server.
Edited, because I recognized to late, that Wikipedia mentions that zeroK-Artwork might also be under CC-by-NC-ND.
Edited again to clarify, that its not open source because of the artwork.