I have never developed a plugin for wordpress but it was my understanding that someone is checking these plugins ...is that incorrect?
This "Timelines" plugin very bad. There's no documentation - he says "no code needed" but that's a nonsensical statement.
The problem is that "Simile Timeline" with which this plugin interacts takes time to understand - it has a somewhat steep learning curve so perhaps there was no one to check this plugin out.
My vote is that it should be removed. There is absolutely no documentation showing how it works and I'm sure that only the developer can make it do what he says it can do - for the rest of us it's a total waste of time to bother with it. Other plugins have maintained a much higher standard than this.