Ah, it's a pretty awesome game - the right amount of complexity and fun. If it was open source it could continue forever like OpenTTD. Then maybe career mode could be completed.
Honestly, this is one of the very few games I've enjoyed in the last 10 years.
OpenTTD is a re-implementation of TTD, though. OpenKSP would be the equivalent (which doesn't exist).
Quake 3 Arena is a better example, which has open source code but proprietary graphics. OpenArena is the open variant.
Or HoverRace, where the developer released the source code but extremely late. The game was abandoned around 2000, community dead by 2004ish, and code released a few years after that. Too late to really save it, but it was still nice to play now and then.
Warzone2100 would be a proper example of an commercial game having a open source afterlife (including being ported to linux/mac and continued development to this very day).
I'm pretty sure KSP will continue. The modding community is strong, and has already created several addons that are more advanced than anything the original devs ever wrote.
Honestly, this is one of the very few games I've enjoyed in the last 10 years.