Would be feasible to use Saxon 8 under JRE or JDK 1.3?
If necessary any additional JAR can be put in the classpath.
I would like to run Saxon in an environment where no JRE 1.4 or higher is available.
I have tried XSLT 2.0 compared to XSLT 1.0 and the improvement is high, even though I know still little about 2.0. It's hard now to renounce because of JRE limitations.
I originally made Saxon dependent on JDK 1.4 because of the need for regex support. Paradoxically, the regex services are now accessed through an abstract interface that could be provided by a separate JAR library. In the meantime, however, Saxon makes very extensive use of the CharSequence interface for passing strings around. This interface was introduced in 1.4, and because Saxon depends on the fact that java.lang.String implements CharSequence, it's almost impossible to retrofit this to JDK 1.3 without very substantial redesign of interfaces. So the short answer is no, sorry.