Log parsers are plain Java classes extending net.sf.logdistiller.LogEvent, declared to the core engine with a logdistiller.properties properties file.
A sample custom log parser extension is provided in sample/ subdirectory. More explanations are available in LogTypes Extensions Center
If the log parser you need is for a publicly available tool, I'll be happy to develop and add it to the base log parsers included in LogDistiller distribution. You just need to fill a feature request and give me some sample logs to work on.
To be developed... ask on the mailing list if you're interested, and sample/ directory is not sufficient.
Plugins and publishers are extensible too, but this is less common: principles are the same as logtypes. See Plugins Extensions Center.