Yeah, I'm not sure either. The <description> tag in the pom says "Adapter version of JUEL without dependencies to javax.el". That just explains what has been done, not really why.
The commit log says: "ACT-189 activiti-juel added, based on Apache-licensed JUEL 2.2.1 to allow method-invocations with params in expressions, even in old EL-environments" which provides a bit more information.
But not being on EL expert, I can't provide more information …
Anyway, unless someone shouts quickly, I'll change the version number, as having non snapshot in a tree is really bad (nearly as bad as having SNAPSHOT in a tag).