A lot of the delays are discussed in the Mag, but the cliff notes version is:
The game was originally built in Unity, but after the team decided to expand their vision, Unity simply couldn't handle the workload without massive framerate issues. Spring/Summer 2013 was going to crowdfund the Unity version, but after Epic unveiled UE4, the team decided to reconsider and learn UE programming. They spent two years rebuilding the game to take advantage of UE4, which comes across in the latest batch of screenshots.
They then shot for Feb. 2015 to crowdfund, but Microsoft reached out about bringing the game to Xbox One, and Sirenum decided it would benefit the campaign if they could promise PC and Xbox One support right out of the gate. They expected it to take a month or so to complete the paperwork, so they pushed to March 20. Paperwork didn't move as quickly (working with MS and Sony is never a quick process. I'm coordinating some Cover Stories for the rest of 2015 that have taken a LONG time to get approved. It's not difficult, and it's not like they're trying to be a pain, they just have a lot of moving parts and a million people have to sign off on any given decision.) so it then became April 2, as cited in the Magazine.
The latest delay is related to a partner they brought on to help make good on the Kinect-related promises they're boasting. (Which, frankly, I was very skeptical of initially. I think that comes across in my interview. I didn't pull any punches with Sirenum, and they were good sports for taking it in stride and answering candidly.) The team knows they're asking for a LOT of money, so they want to launch the campaign to coincide with a major media push. (April 2 was to coincide with the Mag release, which didn't pan out. Late April coincides with a Microsoft conference.)
Sorry, guess that's not the cliff notes version after all. But that's basically how crowdfunding has gone up to this point.