What do you mean with "compatible"? DB2 V9.5 for Linux, Unix, and Windows runs on those platforms. So you can simply install and use it.
p.s: There are 3 other DB2 products (different from DB2 LUW): DB2 for iSeries (AS/400), DB2 Everyplace, and DB2 for z/OS. Those won't run on a Linux system (maybe DB2 Everyplace does - I don't know).