Star Trek Alpha Quadrant : Steven J. Ege : Free Download, Borrow, and Streaming : Internet Archive
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A free OGL unofficial fan-made Role Playing Game set in the Star Trek Universe

These are some high quality, fan-made rules for Cepheus Engine (and so based on the Mongoose Traveller SRD) covering various Star Trek shows up until 2017 (TOS, TAS, TNG, DS9, ENT).