There’s no small amount of time traveling going on in Diversionary Theatre’s production of Sarah Gubbins’ Fair Use,a winning romantic comedy that opened over the weekend in University Heights. Even though the two-year-old play, dealing simultaneously with a bi-gender love triangle and the sticky question of creative license, is set in the present, its nods to the past are many: a subplot (more like the proto-plot) that borrows “Cyrano de Bergerac’s” love-letters device; a recorded music soundtrack that echoes the noir romance of the ‘40s (including the use of the seductive title track from the film “Laura”); the early-‘70s plagiarism battle between the Chiffons and George Harrison over “My Sweet Lord” and its similarity to the girl group’s “She’s So Fine”; and, for sheer anachronistic visual impact, how about the sight of an old manual typewriter on the otherwise contemporary Chicago law-office set?

But if director James Vasquez messes with our heads a little, he also elicits smart and likable performances from Fair Use’s solid cast (led by Amanda Sitton) and moves Gubbins’ story along at a crisp clip. If the ending feels abrupt – and it does – we can’t really complain, because we’ve had a ball almost all of the way getting there. Credit not only the statuesque and sympathetic Sitton, but the sharp comic turns by the rest of the tightly woven ensemble: Wyatt Ellison, Jacque Wilke, Wendy Maples and Stephen Schmitz.

Sy (Sitton) and Chris (Ellison) are fellow attorneys (she’s gay, he’s straight), and they have something in common besides working for the same law office: They’ve both got it bad for legal colleague Madi (Wilke). Chris is more interested in Madi’s physical attributes, which are impressive, while Sy admits to confidante Bec (Maples), a lesbian case researcher with a wisecracking mouth, that she’s been in love with the straight but (she believes) curious Madi for 10 years. Nodding to “Cyrano” and many other stories, written and filmed since, Sy begins writing (on that manual typewriter) love letters to Madi for the smitten Chris. The ensuing reaction, and discovery, are inevitable. It may not have been Gubbins’ intention to reinvent the wheel here, but she does have the gay-or-straight dynamic going for her.

Then there’s the side story, about a novelist (Schmitz) who’s being sued by a hack mystery writer who believes his manuscript has been plagiarized. Sy, Chris and Madi take his case. While the converging questions of copyright, creative inspiration and, yes, fair use, are thought-provoking (particularly in parallel with Chris using letters written by Sy, at first without her consent, to woo Madi), the legalese all kind of runs together and the culminating conclusion, that everyone’s a plagiarist, isn’t as startling as it is meant to be.

The three-sided triangle is the fun of Fair Use, and director Vasquez allows his actors some excusable over-emoting and moments of physicality that keep the proceedings light and make this a story without either a bad guy or a fall guy. It’s feel good for all – even for the nerdy, panic attack-prone novelist.

While the music is atmospheric, it’s also intrusive in spots. But the various props that bolster the action on an otherwise static set (an office basketball hoop, a bicycle upside down and under repair) are effective and the use of darkness and light well conceived.

This is not a message show, but don’t be surprised if this thought occurs to you at some point: All’s fair – in love and in literature.