Both World Editor Unlimited and Jass NewGeneration Pack use a process of memory injection to operate. The result is that some AV software will detect both as a virus when in reality they are completely harmless as they are doing exactly what you want. The false positive is generated because they start a process which modifies the memory of another process, a practice that should never happen in proper software but is required because the makers lacked the source code for WorldEdit so could not modify it directly.
That said, make sure you download both from trusted sites.
Examples of trusted sites...
HiveWorkshop
WarCraft3Campaigns
TheHelper