XBMC and Media Center PC - did one steal the idea off the other?

im not totally sure on what exactly Media Center does and doesnt do but its features seem to be very similar to that of XBMC.did they steal the idea (or even use the source code being as its open source) and claim it as their own? i know its not beneath them especially from someone who created a program for modded xboxes.or was that released first and XBMC stole the idea from Microsoft? or was it just a coincidence?