I'm not sure if there is a free-to-download-and-distribute IBM JRE. There are certainly IBM Win32 JREs that are not tied to IBM PCs and if you own certain IBM products, you can redistribute the JRE as per their terms.
For example, this excerpt comes from the pithily titled IBM Rational Application Developer for WebSphere Software 7.5.2 GA license:
DISTRIBUTION OF JRE REDISTRIBUTABLES
You may distribute the software listed
below (the "JRE Redistributables")
only in conjunction with Your
application and subject to the
following terms: (1) Your
redistribution of the JRE
Redistributables must be in object
code and must comply with all
technical and user directions provided
with the Program; (2) Your application
must redistribute other
Redistributables identified in this
license with the JRE Redistributables
unless Your application is designed to
run only on general computer devices
(e.g., desktops and servers) and not
pervasive devices; (3) You may not
remove any copyright or notice files
contained in the JRE Redistributables;
(4)You will indemnify IBM or third
parties that provide IBM products
("Third Parties") from and against any
third party claim arising out of the
use or distribution of Your
application; (5) You may not use the
same path name as the original
files/modules; (6) You may not use
IBM's or Third Parties' names or
trademarks in connection with the
marketing of Your applications without
IBM's or Third Parties' prior written
consent; and (7) IBM or Third Parties
provide copies of these files or
modules "AS IS," i.e., You are
responsible for all technical
assistance for Your application.
In Your license agreement with the
recipient, You will notify the
recipient that these files or modules
may not be 1) used for any purpose
other than to enable Your application,
2) copied (except for backup
purposes), 3) further distributed
without Your application or 4) reverse
assembled, reverse compiled, or
otherwise translated.
The JRE Redistributables software can
be found in the following directory on
the installation media:
/jdk/jre
You can lookup/search IBM software licenses at http://www.ibm.com/software/sla/sladb.nsf.