Eh, I guess we'll have codenames for internally referring to the Sphere projects.
As a point of consistency, the official name of the official "vanilla" version of Sphere, whether on Windows, OSX, Linux, iOS, Android, whatever, is the
Sphere Game Engine, or
Sphere for short.
Sphere also refers to the working API and formats for devs to use when making their projects, therefore a
Sphere-compatible project is a project that should work on all variants/forks of Sphere itself and all engines claiming to be Sphere-compatible because it doesn't rely on enhancements to either API or formats not available to the "vanilla" Sphere engine.
Vanilla Sphere is the codename of the official version of the Sphere engine; the current Windows Sphere, Mac Sphere, and Linux Sphere all share this codename so we've been using Mac Sphere and Linux Sphere to refer to the *nix variants and just Sphere to refer to the original Windows variant. Vanilla Sphere on all platforms uses Mozilla SpiderMonkey for JavaScript and attempts to use native OS capabilities for I/O when possible and falls back to SDL otherwise depending on the OS. I wouldn't mind calling the shared codebase of OSX and Linux Sphere's "XSphere" though
A slew of devs over the years have done work on vanilla Sphere at various points.
TurboSphere, or TS for short, is Flying Jester's (mostly) Sphere-compatible engine with non-standard enhancements (though I wouldn't mind useful enhancements being folded into vanilla Sphere) using V8 for JavaScript and explicitly using SDL for I/O. I'm not aware of any particularly different codename for it since we've been referring to it as TurboSphere, Turbo, or TS.
Sphere SFML, or SSFML for short, is Radnen's Sphere-compatible engine done in C# with Jurassic for JavaScript and SFML for I/O. No other codename to my knowledge.
Web Sphere is the codename of the official version of the (currently incomplete) Sphere implementation for web browsers. It has multiple variants based on the framework(s) being used for the I/O shim.
casiotone started work on a Sphere-compatible engine but it's not complete.
I'm not aware of any other active Sphere-compatible engines in progress before Rahkiin's entry into the field. Personally, as I've said once or twice before on this board I would love for one or more of the newer Sphere-compatible engines to actually
succeed vanilla Sphere since it seems that the barrier to entry for adding to or even maintaining it is becoming harder to overcome as time passes. Radnen's editor is already fast becoming the de facto replacement of the vanilla Sphere Editor for new and old users alike and the only thing really preventing outright replacement is its primarily Windows construction.