Hi! I develop Fork with my wife. We don't have manager, marketing team, designers, etc. We also don't have meetings which makes us more efficient :). So, we don't need too much money to survive. Answering your question, yes, it's a one-time purchase which includes future updates. We may release a major paid update in the future, however currently we don't have plans for that. The license is cross-platform. You can activate, deactivate and reassign the license.