I just tested the new appimage. It still uses an old libraw version here. You can test it using the files from Merging 3 brackets? - #4 by anubis and running hdrmerge -vv (two v, not 1 w). HDRMerge should report cblack: 2048 or 2049 in console output. The appimage still reports cblack: 0 which is the output when using an older libraw version.
I tested on a machine which has an old version of libraw btw.