Integrated gaseous fuel catalytic partial oxidation (CPOX) reformer (401) and fuel cell (467) systems can include a plurality or an array of spaced-apart CPOX reactor units (408), each reactor unit including an elongate tube having a gas-permeable wall with internal and external surfaces, the wall enclosing an open gaseous flow passageway with at least a portion of the wall having CPOX catalyst disposed therein and/or comprising its structure. The catalyst-containing wall structure and open gaseous flow passageway enclosed thereby define a gaseous phase CPOX reaction zone (409), the catalyst-containing wall section being gas-permeable to allow gaseous CPOX reaction mixture to diffuse therein and hydrogen rich product reformate to diffuse therefrom. The gaseous fuel CPOX reformer also can include one or more igniters (435), and a source of gaseous reformable fuel. The hydrogen-rich reformate can be converted to electricity within a fuel cell unit integrated with the gaseous fuel CPOX reformer.