Complex sentence: As this was a closed-source project, Proxomitron is no longer being maintained nor developed; however, the Proxomitron program is still functional, and there is a community of users who provide support for it through electronic forums.
Split into simpler sentences: As this was a closed-source project, Proxomitron is no longer being maintained or developed. However, the Proxomitron program is still functional, and there is a community of users who provide support for it through electronic forums.