Have you read the article? > Two details: the extensions need to be signed by Mozilla, and only US English speakers will be allowed to disable this requirement

Have you read the article? > Two details: the extensions need to be signed by Mozilla, and only US English speakers will be allowed to disable this requirement. This is not what is written there. The addons need to be signed by mozilla. The process is automated. The unbranded version of Firefox is distributed with the English locale. You can install other language packs. Firefox Stable and Beta can't disable the signing requirement. Firefox DevEdition, Nightly and Unbranded can.