Is there any way the source code to just the editor portion of Sublime Text 2 can be made available, possibly at an additional license cost?

I’d like to incorporate the text editor part of Sublime Text 2 in one of my applications.

If by “additional license cost” you mean enough money so that author doesn’t have to work for the rest of his life then probably it’s doable. Otherwise nobody will share the code of closed source application as that would ruin the current businesses model.
On the other hand, embedding compiled binary through an exposed API could be doable, if author finds it worth doing.

It is not unusual for a company to release source code of a commercial product for an additional license fee.
Mindscape for example does it for their product LightSpeed.

Whether or not this is a sensible thing to do for a compony or individual developer, depends (amongst other things) on how innovative the product is and how difficult it is to reproduce key features of the product without the source code.

I think that SublimeText contains several key features (the user interface, multi platform support, etc.) that are fairly unique and very difficult to recreate for the average software developer. Hence, its source code would be quite valuable.
So I don’t expect that SublimeText’s source code will be released. At least not for an affordable fee.