Why does duolingo use عند in this sentence, rather than the correct عنده for "he has"?
If George is not to be mentioned after عند but before it, then it would be عنده
The combination of عند جورج simply translates to (George has), or literally (At George).
Interesting -- so no need to conjugate if the verb comes first. Does that only hold true for odd verbs, like عند , or does it apply to others, also?
Well, this is another thing. The sentence in English uses the verb (has). However, عند in Arabic is not a verb. But an article, and precisely a preposition. The above sentence in Arabic actually does not contain a single verb.
To make things a bit closer to English: you can either say (at George) or (at him), but saying (at him George) might sound a bit cumbersome I guess.
That explains what I get from google ... odd that this was never mentioned in my Arabic classes. I had wondered why it wasn't conjugated normally, but relied on possessive endings.
They should expect it if you say George had a pretty door instead of saying George has a pretty door I'm not saying that the correct answer is with had instead of has I'm just saying they should exept it if you accidentally spell it with a had instead of a has.