You should always include log information / output from the startup when you create a post which contains a phrase along the line of "did not work correctly".
Many projects exist that have forked from the fme data list extension over the years, as the original developer is not maintaining that addon any longer. From where did you obtain those files? What Alfresco version did the source specify the addon to be compatible with? Chances are, you simply picked up a version that is not compatible with 5.1 (yet).
Putting them into the WEB-INF/lib folders was sort-of correct in that these places should be guaranteed to work for any JAR-based addon. There are more appropriate places though as the Alfresco default installer should create modules/platform and modules/share directories directly below /opt/alfresco-5.1 which are intended for those kind of JAR addons.