Strictly speaking, "Fields of Endeavor" restrictions violate the OSD.
However, my guess (and that's all it is) is that in this case, the authors aren't actually interested in enforcing such a restriction, but rather added the "educational use only" line as part of an attempt to avoid any liability for subsequent use of the code.
I had an acquaintance who was sued by Blizzard under the DMCA for creating a game server for StarCraft. That was under Vivendi which they are no longer a part of, so maybe it's different now, but I would not trust them myself.
The people mindcrime was talking about trusting are the creators of Nostalrius, not Blizzard — though of course Blizzard will threaten you for publicly running this program just like they did Nostalrius.
However, my guess (and that's all it is) is that in this case, the authors aren't actually interested in enforcing such a restriction, but rather added the "educational use only" line as part of an attempt to avoid any liability for subsequent use of the code.