DwarfCorp

DwarfCorp is a precedurally generated, open source fantasy real-time strategy game in which you lead a colony of ruthless capitalist Dwarves to discover new lands, and exploit them for profit!

Dig deep into the earth to discover rare gems and ores, and send them back to the motherland in a balloon or ship. Defend your colony with walls, traps, and mercenaries. Promote your employees for their good work, or give them a slap if they get sloppy. Meet Elves, Goblins, Mole Men, Demons and more! Design your company logo and color scheme, and watch your company grow.

You can find the source code on GitHub. It's under the MIT license, but they edited to mention the assets aren't under the license.