Can I use other brand of single brew coffees like ones made for Keurig brewers?

I am interested in this brewer but need to know if I am stuck with Gevelia coffees or if I can use other options on the market. I love Gevilia, but there are too many desirable options from other vendors to settle with a brew system that forces you to just use their coffee. In another light, If I owned a Keurig system and wanted to enjoy Tassimo coffee, could I?