hmm - just did a search myself...
Popoulus is not downloadable but you can get it within this compilation legally (for about 9USD):
EA Compilation:
Chuck Yeager's Air Combat, Space Hulk, Hong Kong Mahjong Pro, Wing Commander Academy, Savage Empire, Seven Cities of Gold, Populous II, Ultima VII: The Black Gate, ShadowCaster and Ultima Underworld (#1)
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Powermonger oth is downloadable...

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You guys remember Megalomania - that was fun too!!