I was hoping they removed the time "bomb" but looks like they just increased it by a year (sept 2019 now I think). Besides that, not sure if there is any other difference.
http://www.r4isdhc.com/KerneDownload/R4i-V3.9b English.zip
http://www.r4isdhc.com/KerneDownload/R4i-V3.9b English.zip