/home/db2inst1/sqllib/db2dump is where DB2 writes diagnostic information. The only potential probelm would be if that writting to that directory causes the instance home directory to fill up, which can sometimes cause problems for the DB2 instance.
I don't know what /home/db2inst1/sqllib/tmp is, but usually tmp directors have no security on them. I assume there is nothing in that directory, or it is of no concern (other than filling up the instance home directory).
Don't know about /var/lum. What is in that directory?