Hello Sina,
We're using the workgroup edition of DB2 UDB 7.1 on NT server. Among the heaps of CD-roms we're receiving for every new DB2 version (7.2 is the current one) there is a CD with the Linux version. So that would answer your first question. I think that IBM willl expect you to pay a license fee, but installing DB2 does not require a specific key (It took me quite a while to take that in !), so technically you can be up and running once you install it.
(further info directly to your Email-address) T. Blom
Information analist
Shimano Europe
tbl@shimano-eu.com