It's probably more complicated than that.
In the old days, BEA/WebLogic - the predecessor for many of these products - would let you download a free evaluation copy with a 60 or 90 day run period. After which the product ceased to operate unless you bought a key.
Since then, pressures from open-source products (such as
JBoss) have caused Oracle and IBM to release "Community Edition" versions of their products. These are often full-featured implementations - minus some of the Enterprise-grade bells and whistles (for example, I think DB2 CE is limited to a "mere" 1 GB of RAM usage). Some of these may be open to commercial use, since they figure that if you need it bad enough, eventually you'll start paying for support and/or the high-end features.
Then there are academic licenses, which may carry slightly different restrictions.
Unfortunately, I can't tell what licenses are available for the products in question.