We are using both at the moment as they have different packages.
Drools has already upgraded to mvel2-2.0.10.jar.
-rw-rw-r-- 1 kevin kevin 608039 2009-06-08 14:52 services/jbrules/lib/ext/mvel2-2.0.10.jar
The only uses of the mvel1 that I can see are JBpmObjectMapper and ObjectMapper, so smooks should be free to use the same version as drools and ignore mvel1.
I'll create a separate task to look at upgrading the mvel1 usage.