RDP was actually developed by Citrix long ago, which is why it works. They called it "MetaFrame". Microsoft licensed a portion of it, crossed out "MetaFrame" and wrote in "Remote Desktop" in crayon.
RDP clients have been supported for a long time, not only in Windows clients, but in Mac (by a Microsoft product), and in Linux as "rdesktop", which is open source and not related to the Microsoft or Citrix codebases.
I remote from my Linux Mint desktop to my Windows server 2008 computer using Remmina RDP client. Do you think I will get locked out of my own computer?