As an option, IBM said if I would release rsyslog 5.8.6 under ASL 2.0, they could release their patch under ASL 2.0 as well. Unfortunately, I cannot do this by just declaring so.
You need to keep in mind that I do not own the complete copyright! Actually, there are a couple of hundreds contributors that I can find in git history ... and there are even more in the original sysklogd, which I can't even identify all. As such, it is simple impossible for me to change the license "on my own".
To reach the current state, I did quite intense research on who contributed what some time (two years maybe?) ago. I concentrated on "easy" files (new ones without sysklogd code) and contacted all contributors if they agree on ASL 2.0. Those files that I got agreement on are now under ASL 2.0. For the "hard" files, I even did some research which of them were still from the original syslogd, which was released under BSD. I replaced these files /code sequences with the BSD version (which is identical), and so could put that under ASL 2.0. But still there is a notable body of code left that needs to be under GPLv3+. Some can probably be changed with more author contacting (especially Red Hat contributions, where I have a general "go" for most things), but some code definitely needs to be rewritten. I guess the additional research takes at least some weeks, with the rewrite taking maybe another month or so.Bottom line: it's far from being easy and there is no pressing need. But I don't want to fallback on the effort just because of the IBM contribution. I would need to rewrite it in any case, so there is no point in merging mainstream.