…by the way, I have just noticed that this firmware has been available since september 2011 (beta) and decembre 2011 (v1.00) on the chinese forum for the DSO203 (same as DSO Quad):
There you can find a version for slot 1 and a version for slot 3 as well as some explanations about the menus.
Patrick
PS: I have no idea where the source code is… on source-ds203.googlecode.com it’s still 2.51