Radiant Systems, whose product line includes POS software, more than doubled its net income for the first quarter ended March 31 while revenue rose by 10 percent. Net income hit just under $6 million for the most recently ended quarter, compared to $2.6 million a year earlier. Revenue rose to $87.1 million, up from $79.5 million. Subscription revenue, which hit $11.7 million, was by far the strongest performer as it registered a 28 percent increase over the same quarter in 2010.