Mango is a T-Mobile network MVNO. I think it's always been owned by Red Pocket, but they've changed the way the plan is distributed. (Now through Red Pocket's site, as you've linked.) I thought perhaps it was organized to be marketed through independent phone stores, but there isn't much presence around me.
Definitely some interesting features of the plans-- the international calling credit, global text, and 2G fallback data at 128K. Depending on one's needs, might be a good MintSim alternative.
Yes I think they were always a redpocket thing. The plans actually look pretty good to me. $135 a year for 500 mins/unlimited texts/1gb a month with unlimited 128k data is really good. Mint sim was always a bit too much for me and this fits the middle ground. I wonder if cellnuvo will be able to pay for it... Seems likely as they have a guest payment area which requires the phone number. Edit -Chat says they can recharge the monthly plans via guest checkout but not the annual ones.