You can also browse the following online resources:
syslog device configuration guide (off-site)
deutsches rsyslog forum (forum in German language)
And don’t forget about the rsyslog mailing list. If you are interested in the “backstage”, you may find Rainer’s blog an interesting read (filter on syslog and rsyslog tags). Or meet Rainer Gerhards at Facebook. If you would like to use rsyslog source code inside your open source project, you can do that without any restriction as long as your license is GPLv3 compatible. If your license is incompatible to GPLv3, you may even be still permitted to use rsyslog source code. However, then you need to look at the way rsyslog is licensed.
Help with configuring/using