But I think it is too late for opening it. There is no community left so there is nearly no one who would develop SkyOS.
For me there is only one conclusion: SkyOS is dead!
Actually, I think most new open source programmers look for a project that seems nice and that really needs developers. It is these programmers who could keep developing SkyOS in the future.
Why should they? Wouldn't they rather choose an OS like Haiku or ReactOS? They could do something now and not wait until eternity for SkyOS.
Open Source is not something that works ever. Every oss project has an core team of developers and some contributers but it is not very easy to get a core team if it is not the original one. So it will take a lot time to form a new team, create related documents and so on.
And because of the actual situation there is nearly no interest in SkyOS, so you would need some sort of marketing campaign first to get potential devs looking.
I hope that I am wrong but I don't think it will work now. It is too late.