The open-source software movement has transformed the way software is developed. It has leveraged the power of software reuse with sustainable community support to attractively develop and scale software for the benefit of all. The movement has found its way into the space domain where newer players are stepping in and adopting open-source solutions for both ground and space segments. A notable adoption driver are the recent developments in off-the-shelf compute capabilities of modern spacecraft coupled with the increasing decision-making complexity and data-generation capacity of modern satellite payloads. The latter requires ever more on-board autonomy due to communication bandwidth limitations with the ground control software and the inherent human factor limitations in decision-making. Software which was never expected or even intended to be used in the space domain is now being adopted by space players, particularly in New Space. In support of industry and academia to explore and experiment with open-source for space operations, the European Space Agency (ESA) launched the OPS-SAT Space Lab in December 2019. The spacecraft is an open innovation platform in the form of a 3U CubeSat in Low Earth Orbit (LEO). OPS-SAT has accomplished many firsts in space powered by open-source and rapid prototyping, from the first securities trade to pioneering the use of Artificial Intelligence (AI) frameworks for Machine Learning (ML) training and inferences with payload and telemetry data. This paper presents lessons learned and a suggested way forward from the perspective of two former OPS-SAT Flight Control Team (FCT) members turned experimenters, showcasing the opportunities and challenges in revisiting how spacecraft operations benefit from a rethink with open-source software as a pillar of mission design.