A few months ago saw confirmation that a Booster Gold movie is in development with Arrow and The Flash's Greg Berlanti eyed to direct the film.
"As of right now we have no connective tissue to those worlds," Berlanti told Vulture when asked if the Booster Gold movie would be part of the DCEU that includes Man of Steel, Batman v Superman: Dawn of Justice, Suicide Squad, Wonder Woman and Justice League. "It'd be a separate thing."
Greg Berlanti also let it be known that the Booster Gold movie materialized from the once-planned Booster Gold TV series originally set for SyFy that "never got off the ground." Berlanti and Andrew Kreisberg got into talks with Geoff Johns, DC's new president and co-chief of the films, when the idea of doing a Booster Gold movie came up. Johns also happened to write a Booster Gold comic book series for DC Comics.
Zack Stentz is writing the Booster Gold movie, who penned X-Men: First Class, Thor and the upcoming Power Rangers. Stentz also wrote a Season 2 episode of The Flash, is writing episodes for The Flash Season 3, and also has been elevated to consulting producer on The Flash.
Regarding Booster Gold not connecting to the Justice League movie universe, it is disappointing news in that we won't see Batman interacting with the character, etc. More than likely we'll get a few nods to the Justice League characters, just that the characters and actors won't be featured in the movie. However, it does give Booster Gold a lot of freedom, which should end up being a rather unique movie. And who knows? With Booster Gold being a time traveler and such, the potential to appear in the DCEU down the road is always there.