I haven't had much time till recently to dedicate to my application lrzip, but I have a soft spot for it since I use it extensively so I couldn't let it go to bitrot, and luckily I'm between other projects so have spent a few days on it. Here is an updated version with numerous bugfixes, some for security issues, some for crashes on corrupt archives, some to avoid creating corrupt archives, some for build issues, and random other bugfixes too numerous to list in detail. So this is a stable bug release and I encourage everyone to update.
Downloads, including access to standalone static binary:
The only change to its behaviour is it now requires liblz4-dev to build because it uses the super fast lz4 compression algorithm for compressibility testing - it does NOT use it for any compressed archives as this would be incompatible with the existing format, and almost certainly will not offer any advantage in speed over lzo because the bulk of the time is the rzip pre-compression library stage. It also now can build the crc checking as an assembly component on x86_64, though this is largely not going to affect speed in any significant fashion. Long term I will probably remove this ancient and not-very reliable checking from future versions if I break the existing format. I will also probably drop MD5 sums.
Peter Hyman has also been working behind the scenes to add countless little features to lrzip for the duration that I haven't given it any attention and has been running his own tree with all his changes.
Alas most of those are new features and break the existing lrzip file format, and have come with new issues of their own that would require quite some effort to blend into the existing codebase and iron out bugs. I'd also want new archives to be created compatible with older versions as much as possible preferentially so compatibility code would need to be added.
Thus I concentrated entirely on just bringing out another stable release before looking at any of his code, including having to roll back some of his changes I'd already incorporated into my master tree. In time I hope to get to his changes to incorporate them.