An article on Tripwire's experiences with Unreal and Linux:
http://www.gamingonlinux.com/articles/tripwire-on-why-red-orchestra-2-and-rising-storm-wont-come-to-linux.2021

The Unreal Engine 2 build we use for Killing Floor has a linux build.  The Unreal Engine 3 build we use for RO 2/RS does not.  Newer builds of UE 3 have Linux/Mac support however they are greatly different from our build.  We are looking into what it would take to bring what we need from the newer builds into our engine without breaking everything.  It may turn out to not be worth the cost/effort.

So you can definitely make UE3 work for a new Postal game but you do need to be careful.

When it comes to certain updates that have gone into the Steam releases of Postal and Postal 2, I would like to know how things currently stand when it comes to the notion that some of these features will eventually be implemented into the Desura releases. Obviously Steam integrated features will never see the light of day elsewhere (that is understandable), but I would like to know if/when things like the widescreen support and certain bug fixes that have been mentioned could be added to the versions sold on Desura.

I bought the games on Desura because I wanted to support both Desura and RWS and for me Steam is not an option due to ethical conerns, so I would really like to know if/when such things could make there way to Desura. I understand this not being a big priority with Steam most likely bringing in the most revenue for you guys, and that such things probably wont happen until you are done fixing up the Steam versions so that you do not need to keep maintaining two different code versions, but I still would like some official words on this.

I also notice that it is called "Postal 2" on Desura now rather than "Postal 2 Complete". I am curious as to why you opted to change the name?

You don't need to port dos games, you already have dosbox!

Well, you still can... a native port is always going to run better than something ran through an emulator. Personally though I would prefer more source code releases for older games than re-releases (although you still need to get the data somehow).

Haven't played rapelay in a few years,it's one of those games where you have to take a shower after playing it so you feel less guilty.

Then why play it? Believe it or not I do not play games to feel guilty, and I never felt that way about Postal.

But yeah, a Linux version of P1 would make it on there if any did.  The Linux version is the most Stable too from what I've seen, all works as it did back in the day, where as Windows and Mac have a few minor visual issues.

Linux version runs fine for me as well except for the Challenge missions, which outright fail to load for me.

Event if poeple who bought it on GoG and Desura are going to be very annoyed.

Well, I would not be too annoyed as long as the Desura version became free as well. Plus I did only grab P1 on Desura last summer when it was on sale.

You can buy both games off of Desura and get a Steam key as well as a Desura key for Postal 2. Most inclusive way of getting it.

Some really nice games were in that bundle though. 

Nice. 

Some elaboration by icculus on the Dungeon Defenders port:
http://www.gamingonlinux.com/index.php?threads/icculuss-thoughts-on-unreal-engine-3-games-on-linux.1593/