Sphene first went into development in 2018 while I was in Project Beast as a simple experiment to see if SCM could be parsed in MTA and enough logic could be implemented to run it. This was the case and a simple test script was run (https://www.youtube.com/watch?v=TBsQSw7B_XQ). Its development was slow at first but picked up significantly towards the end of 2020. Our current plan is have enough implemented to have a few fun/memorable missions working (Wrong Side of the Tracks, Breaking the bank at Caligula's, Black Project, etc...) and then open up a server that specifically allows you to try out these missions.
Afterwards we keep continuing implement more logic and getting the entire storyline itself to work from start to end while further fixing issues and adding improvements after. Only after that stage will we introduce our ultimate goal which is adding a Co-Op experience on top of the storyline. We unfortunately are not able to estimate when this would happen due to the complexity of the project and the fact we have our real life obligations that at times can eat up more time than we'd like.
Note: Sphene is going to be open sourced at some point. When this happens during the timeline described above I do not know yet.
Also, I want to take the time to thank @GTX for all the contributions he has made to Sphene since the moment he joined the project back in 2018.