The log files are only 4k each. I'd leave 'em alone.
Maybe dowload Mac Janitor form versiontracker? It runs the daily/weekly/monthly unix clean-up tasks, and might clear those out, but really, they're harmless.
I'm thinking the insatllation plan (?) files might keep track of updates? would software update go screwy if these were deleted, or does it only require the recipt.pkg files?
CV