Yes, you're correct it's called a donation. Not really sure what you mean by add your own channels, but when you make a donation the channels you get are what they stream. I've been doing this about a year. This site is helpful.
When I joined there were very few HD channels, now most if not all are, however, there have been problems lately (2-3 months) with much freezing and missing channels. Very hard to use during the evening EST. Just read the posts.
Hope they get it sorted soon. The moderators here are helpful and I tip my hat to them.
As far as I'm aware (please correct me if I'm wrong) the 3 services represented here are dependent on the same source for signal so if one is crappy, they likely all are. I'm with IPTV66
Good Luck
