As an experienced full-stack developer with over 9 years of working in various projects, I assure you of my qualified capabilities to handle your task. My expertise in Python/PHP/JavaScript and Django/Laravel/VueJs/NodeJs make me a perfect fit for your cross-platform software project that requires both image, video, sound editing, creation and AI integration. It's relieving to know you are open to exploring existing open-source codes; this is advantageous as it allows for flexibility and cost-effectiveness which aligns with my job approach.
Moreover, having an entrepreneurial background has given me a unique perspective in understanding the value of starting projects from scratch and the strategy required for their success. I am absolutely confident in creating scalable, high-availability web applications- a trait crucial to dealing with multimedia editing software where large volumes of data are the norm.