
That means the version you get from minetest.net is too outdated to use with this version of the mod.
Solution? Use WorldEdit 0.6 for Minetest 0.4.7, but be be aware that it doesn't have the orders-of-magnitude speedups and the bugfixes that came with 1.0. Or better, switch to a newer development version of Minetest! You'll get a ton of new features too!