Set some 4000 years before the rise of the Galactic Empire, the time period has been explored in video game format with the hugely successful RPGs Star Wars: Knights of the Old Republic and Star Wars: Knights of the Old Republic II - The Sith Lords, along with the MMORPG Star Wars: The Old Republic. According to AICN's source, former Bioware writer Drew Karpyshyn (whose credits include KotOR and Star Wars: The Old Republic, as well as Mass Effect and Mass Effect 2) is rumoured to be working on a script for Knights of the Old Republic, which is apparently the hot topic of conversation around the water cooler in Bioware's offices.
Now, while it's likely (if not certain) that the idea of an Old Republic movie will have been tossed around at Disney and Lucasfilm, it should be noted that there are several Star Wars projects currently on the go at the moment, not least J.J. Abrams' Star Wars: Episode VII. Furthermore, AICN's last Star Wars scoop suggested that Disney's first standalone feature would centre on Yoda, a story they reported just one day before it was revealed that Lawrence Kasdan (The Empire Strikes Back) and Simon Kinberg (X-Men: Days of Future Past) were working on Han Solo and Boba Fett movies. So, I'd probably take this one with a pinch of salt for the time being...
Update - Well, that didn't take long. According to Karpyshyn himself on Twitter, he hasn't heard anything about a Knights of the Old Republic movie. So, it would seem thats another Star Wars rumour we can chalk down as pure fiction.