The distributable WED is a more limited version of WED called WEDS instead. It is only for those who have Pro edition. If you want an in-game level edittor, you could script one yourself. Just knowing the four fundamentals to scripting and use of ent_create and ent_remove is all you basically need.
"You level up the fastest and easiest if you do things at your own level and no higher or lower" - useful tip
My 2D game - release on Jun 13th; My tutorials