EnderIO and Mekanism seem to have the ability to convert MJ to RF. This conclusion is based on forum chatter, I cant find definitive docs that support me. They seem to be actively developed (both have recent commits to their github repo.)
Mekanism seems to be pretty heavy with a lot of additional machines and items. The wiki seems pretty lean with missing entries.
EnderIO looks to be more specialized in the realm of item/power/redstone/liquid transportation. The wiki seems somewhat immature, but the content that is there is nicely done.
