maybe a little fear of embarrassing myself by breaking something

ha ha no. you think you have direct access to the live code? ;-)
You submit patches (which are really full revisions, not deltas). We do a code review. If we see any potential issues, we throw it back to you, with discussion. Please don't be afraid of the process, whether out of vanity or any other reason.

How hard would it be to build and run a clone/development version

I'm not sure of the precise answer, but I believe it's in the vicinity of "very", unless we don't mind giving away the passwords to every account; in that case, it would be "not at all". :-)

Is a dev deployment a possibility? Even one without user accounts and posts—just the stored code—would be fine.

Update: I don't think the second half/answer was there when I started to reply. So the question is probably moot. :P

It should be. Someone ;-) should investigate. I feel like it's been done before...

Note to self:

The only user installed by any extant nodeballs was 113. Users 112 and 111 were not, afaict.

(The only other NPC users after 113 were 519 and 827, and they were not installed from nodeballs either.)

The significance of this is that, if we do create a "safe" copy of the nodebase, we can probably safely delete all users except root.

I reckon we are the only monastery ever to have a dungeon stuffed with 16,000 zombies.