Projection Issue: Interrupted Sinusoidal to Equirectangular

[Asis]

I've got a interrupted sinusoidal map (a gore map, I read somewhere), and I'd like to make it equirectangular. Problem is, I don't know how and I don't know where to look anymore.

The map has 12 sections of 30°, and the WIP thread is here. I will also attach the map at the end of this post.

While I have come across a couple of promising looking projection programs, I haven't had much luck with them. I just can't get my head around Geocart, though it does look like it can do precisely what I want it to do. I was trying out the demo, so that may have been why I didn't get it to work. waldronate's ReprojectImage does do sinusoidal, but not an interrupted one (at least not as far as I can see).

I've seen GDAL and QuantumGIS mentioned, but I have no experience in using a command line interface, and I'd rather not look around for ages and try to learn a new software if it turns out it can't do what I'd like after all.

Other projection software I've come by only accept equirectangular (which is why I want the projection in the first place).

Maybe I'm just being slow and the answer to this is right in front of my eyes. If you know how, please do tell. I'd really appreciate it.