That's pretty cool. I'm impressed by the lack of CA in that image. Hopefully the CA correction is better than that earlier report (that said it was about on par with a regular F/5 achro) suggested.
the german forum thread has developed a bit - Tommy Nawratil has taken his example apart, found an adjustable but plastic lens mount and ground down a spacer a bit to remove some SA...
and then measured the secondary spectrum for the 102/460 and an SW 102/500.
As can be seen the result is comparable to the f5 FH and Gerd Duering did some rough doublet designs for FK61 and cheap CGEM partner glasses - all were better by a huge margin.
Here is the values for some existing refractors, achros and apos alike...
Everybody has to draw their own conclusions from this - but I would not buy the scope for the ED glass but rather for as a 4" richfield FH with a nice focusser.