Is there any concurrent company on the market?

There are several 3D virtual reality platforms available online.
Some of the most popular are:
[1]Active Worlds Developer: Active Worlds
Release date: 1995 (beta), 1997 (public release)

[2]There (Internet service)
Developer: Makena Technologies
Release date: 2003

[3]Entropia Universe
Developer: MindArk
Release: 2003

[4]Dotsoul
Developers: Joseph Bergeron and Laura Herrmann
Release date: 2006