> It also bothers me that they didn't just use the GPLv2
Maybe they want people to be able to easily distribute binaries of the software via BitTorrent. Apache allows this, the Vim License allows this, GPLv2 does not[0].
Well, it could also be used under the terms of the GPLv3 (because the Vim license allows you to license it under the GPLv2 or later). Most people don't like the GPLv3, which is why I didn't mention it (even though it is a superior license in many ways).