FWIW, the Starbound source code was leaked a while ago, and since then, some community projects have created inofficial builds of the game, with additional bug fixes and enhancements. Search for "OpenStarbound" or "xStarbound".
Back in 2014, the Chucklefish founder said they'd open-source the game some time after release, but as the leak went public, Finn deleted his tweet. With the source being public, but still proprietary, this creates a grey area. CF most probably won't go after community projects for the time being, but this may change once their IP get bought up by some larger company. If they'd properly release the code under GPLv3 for example (whith third-party code like the - already dysfunctional - Discord and Steam APIs removed), this would create legal safety and give people an incentive to buy a copy of the game to acquire the resources for playing.
Looking at the source, it's relatively clear why they've abandonded the game. Even the community, while normally quick to improve things, struggles to keep the source in a working condition after changes, as the architecture and code quality is really sub-par for the gaming industry. I mean, they were young, inexperienced and even used unpaid interns under the age of 18 to write the code, which led to a huge shitstorm in the fanbase. The Xbox port failed because they couldn't get all the changes in there, including controller support (for example, key codes are directly checked/addressed within the game code where each action happens, not tied to virtual actions as they should've been). Then there are a few C++-specific design issues, resulting in huge executables, long compile times and hard-to-read code. TBH, it would be faster to rewrite the core game code instead of trying to fix/refactor it.
