Firefox 38 includes a new feature called DRM. The original DRMs come from the Digital Rights Management which means Digital Rights Management.
Its content Digital Rights Management is encrypted and usually protected from all copying, since it is not open source (this means that no one knows what the code of the new feature contains).
Purpose of the system DRM that exists in Firefox is to provide you with the ability to play protected video HTML5
DRM is a proprietary technology, so some users may not be too happy at the thought of it being on the open source web browser their. No one knows how it works and what to do at any given time.
Although the Mozilla the DRM addon put it in a sandbox wrapper, maybe there are many who wish to get rid of it.
Of course you can disable it, as the developers of the application implemented it as a plugin that can be removed. But some may not want to "tease" their application.
Mozilla probably thought the same and released a separate version of Firefox without DRM.
From the following links you can download this version for Windows in Greek or English.
