A little brain storming can be a fun learning experience.
Agreeing with the above posts: no good reason to sell DomainNamesCanada and the words web hosting canada in the way used are too generic to be an infringement.
"black sun" is a nice sounding brand but don't know anything about the company otherwise.
DN.ca is a two letter exact initials domainers dream The only reason to keep DomainNamesCanada.ca is for defensive purposes since it is the description of the forum. The chances of that domain getting developed and causing problems is low, especially in the .ca space but personally I would choose to avoid the possibility.
If you check what is getting picked up these days on the TBR, which is everything, it will likely get picked up and perhaps one day may ride the on the coattails of DN's popularity
Not a fan of using "Canada" in a domain overall but it may work for Canadian international companies who can't secure exact .com and like their canadian identity branding.