Pg.62 Races of Faerun states that half-drow have the following regions: Dambrath, Elf (drow), Half-Drow, The North.
Out of all of these Dambrath and the north are the most straighforward. Dambrath is a country detailed in the Shining South Faerun campaign book, the short version is that it is a surfacer country ruled by half-drow. The north is also a relativly simple explanation except its an entire region, not just one country, its also a region that shares parts of the current map on the server. The Greypeak Mountains are considered part of The North as is the High Moor, Misty Forest, and Serpent Hills. The sword coast is made up of The North region and the Western Heartlands, being that The North is part of half-drow's source book choices for regions it really would be fitting that they are allowed to be surfacers, because well that is what they primarily are in all sourcebooks.
For the Elf (drow) region you actually have to look at Pg.34 and Pg.38 of Races of Faerun. Page 34 states regions: Elf (drow), Cormanthor Drow. And in Pg. 38 it gives an example of a surface dwelling drow from Clan Auzkovyn or House Jaelre. So the Elf (drow) region is almost self explanitory, it's the underdark. So yes absolutely half-drow should be able to be an Underdark character. But the same also holds true for bieng a half-drow from the Cormanthor. Now Pg. 38 has a bit of subtext in it, using two vhaerunite drows clan's as examples it does not explain that Clan Auzkovyn during the timeline the server is set would be living in the High Forest not the Cormanthor. Clan Auzkovyn moves to the Cormanthor after they loose their war with the wood elves in the High Forest. The high forest is of course part of The North, but the book does not actually clarify timelines.
And the unclear and interesting bit the Half-Drow region. The thing is it's not actually clearly defined in any book what the half-drow region is. So, what exactly is it? Well, we know its at least not Dambrath, Elf (drow), Cormanthor Drow, The North. Because those already got their own entries, there really is no point in stating the same thing twice in one entry. Now there are a few sentences within the text that could potentially explain what it is, though really its my opinion and conjecture. Though fair warning what is written is pretty dark.
The book reads for their origins
The language choices that half drow get on Pg. 62 of Races of Faerun says thus
But this all leads back to how the server treats half-drow, which is the exact same as drow. Even though canonically it's not the same, there are more half-drow on the surface than in the Underdark. Half-drow according to sourcebooks are a surface race that has the option of being from the underdark. They are not baby monsters that are locked away in the deepest depths of the earth never to see the light of day. So really I am only asking for what is already written in sourcebooks, and the server already comes in contact with one of the region's a half-drow has access to. How the server portrays half-drow right now is just inaccurate, and really weird when you can play grey-orcs on the surface.