Logs and Image copies are not compatable. If you have the correct version, you could extract data from the backups.
If you have DB2 for z/OS or 390 version 7 and above you can use the unload utility to extract the data in external format and download it to the DB2 for LUW server for IMPORT. However, you will still have to map the data file for importing into DB2 for LUW, and things like "nulls" can sometimes be tricky.
"If the specified image copy data set is a full image copy, either compressed or uncompressed records can be unloaded. If the specified image copy data set is an incremental image copy or a copy of a partition or partitions, you can unload compressed records only when the same data set contains the dictionary pages for decompression."
Another option is DB2 Replication between DB2 mainframe and DB2 for LUW. If you try this, I would recommend that you upgrade to fixpak 6b if possible. I don't know of any specific problems with fixpak 5 with regard to mainframe replication, but there are always lots of replication APARS fixed in each of the fixpaks.