Yes this is rather confusing to say the least. But there are a number of articles that explain what is going on. It stems from the past where Chapman kept his car company separate from his racing company, giving us now what is known as Group Lotus (cars) and Team Lotus (racing).
Tony Fernandez, the Lotus Racing boss, secured the rights to use the original Racing team name "Team Lotus" for his F1 team from David Hunt the owner of the racing brand name. However,Danny Bahar and Group Lotus (cars) have come on the scene and things got complicated. Here's a good article about the history from the TopGear site.
F1 2011: It?s Lotus vs Lotus - BBC Top Gear
Renault sold off the majority of their shares in the team to Genii Capital who are a Luxembourg based investment group. Genii and Group Lotus have partnered up to form "Lotus Renault GP" with Group Lotus taking a major stake in the team.
News - Group Lotus + Renault + Genii = Lotus Renault GP
There has been quite a bit of legal ongoings regarding the Lotus name as Group Lotus (Proton the parent company and the owners of Group Lotus and the brand) attempted to prevent Fernandez from using the Lotus name.
I am not sure where this stands at the moment but it could be the reason why the media are not referring to the team as Lotus Renault GP at this time and Group Lotus are appearing to be just a main team sponsor. As you can see by the badge branding the two teams differentiate themselves by the original Lotus and the Lotus Racing badges.
Regardless, who cares? Let the suits sort all of that out as they like to do. It's just great to be a Lotus owner and fan right now and see both brands in F1. Also keep an eye on the Indy circuit and the GP2 and GP3 series as well as the GT2. There is a lot going on right now in the racing world for *Lotus*.