It seems that a recent update of AVG for Android has started identifying any app using Leadbolt ads as a threat. AVG will call such apps a "potentially unwanted program"...
I tend to agree with AVG - A check of the link you gave contains the following info:
"Android/Leadbolt is a software that gets installed on your android device as a bundle with the application you downloaded. It displays unwanted advertisements as notifications and may be considered privacy-invasive. These type of ads are not easily blocked and usually require of either the complete removal of the infected application or another application to block the ads from being pushed. These kinds of threats are called Adware. Android/Leadbolt is currently ranked 38 in the world for mobile, online and PC malware, affecting between 1,000,000 and 5,000,000 users."
It sounds like Leadbolt installs its own stuff on the Android device and is relatively invasive which is the problem. I have encountered a couple of apps that did similar things and I removed them pretty quickly. While not an exhaustive search, I have checked out several other good sounding monetization systems but they all wanted to install their own stuff so I decided against them. If I install an app, I do not mind built in ads such as those from Admob, since I know that is how the developer is trying to support his/her efforts. However, I strongly object to any app that wants to install other software for whatever purpose, including pushing ads. If removal of the app gets rid of the ads as well, that is OK, but if removal of the app does not necessarily remove the advertising at the same time, I feel that is just plain wrong and it sounds like Leadbolt may fall into this category and that is the reason AVG treats it as a threat.