OK, so as far as I can tell, this is based off the DBZ webcomic that I've seen fanart of but have not bothered to read until now.
The story is an interesting concept but for guys like me, a bit of a headache to keep up with. The whole different universe thing really annoys me because it can get really confusing.
As for the flash itself, as good as the animation was, it probably needed a bit more because it felt like some scenes were traced over and had animation added to it like the VGCats comics that were being uploaded here. I even noticed a few errors here and there like when you see the shot of Goten and Trunks talking to the aliens, the hands looked messed up a bit. Which is why tracing doesn't do much good, especially when you add more to it. I mean, there was an old Kingdom Hearts manga animation adaptation that did the same thing and everything looked so poorly animated. Which is why when a comic should be adapted to animation, I think trying to animate panels should be done the same way most manga to anime adaptations do it, from what I noticed. Try having more than just characters standing there. I think adding a little more than what actual comic suggests is a great idea.
As for the music, sure it was remixed but it was fitting. But, I don't think you'll have your animation taken down for copyright laws and such mainly because your not using it for profit. Plus, many DBZ animations from 2003 and later have done it and they're still on the site up until now. So, I don't think you'll get in trouble.
Anyway, this was good for a nostalgia trip (seeing that I haven't seen much of DBZ in a while) and I noticed some improvement. Keep it up and good luck with finding voice actors.