** Shares of Australia's Activeport ATV.AX rise as much as 71.4% to A$0.012, logging their best day since Aug. 14, 2025
** Stock hits highest level since March 6
** Software developer says Barcelona-founded Submer Technologies buys co's GPU software partner, Radian
** Adds, deal to boost demand for co's GPU software, supporting recurring revenue
** Co retains strategic equity stake in combined business valued at over A$1 million
** Stock down over 40% this year, including the day's move
(Reporting by Rajasik Mukherjee in Bengaluru)
((Rajasik.Mukherjee@thomsonreuters.com))