Okay, so, after spending an arduously long time downloading forge/gradle, and then discovering that the package was not working, and the resolving that issue thanks to http://www.minecraftforge.net/forum/index.php/topic,14048.0.html, I have come upon another error:
If I add the dfml flag the JVM arguments (-Dfml.ignoreInvalidMinecraftCertificates=true) I get:
(and I've been unable to find a log that contains the full thing without a ... 6 more)