[concordDance]

There's a bunch of open source successors (e.g. they started as Total Annihilation clones) made on the springrts engine that you may be interested in. I believe both Zero-K and Beyond All Reason are still being actively maintained.

[azalemeth]

How I wish they'd have better os compatibility!

[happymellon]

Beyond All Reason supports Windows and Linux, or are you after a mobile experience?

[OneTimePetes]

Mac OS?