Lets assume you use Debian for argument's sake (I'm a Debian guy, sorry). If you install GPG from any of the common APT repositories, you'll find it requires libusb - because of the smartcard capabilities it has. Not useful on a server. Of course, you can custom compile it, but in practise how many of us do? I know 1 guy out of hundreds. There are thousands of other examples like this, across all distro's not just Debian; be it Fedora, SuSE, etc.
If you have GD installed, again you'll find you have a large number of X libraries already. Seriously, if you're that short on diskspace or memory, then you seriously want to start thinking about the next package up, or upgrading your box.
If you happen to be Gentoo nut, then I assume non of the above will apply to you (unless you happen to emerge everything - in which case, whats the point?), but then thats your own fault for spending your life compiling every little thing ;-)
tbh, if the community got together and created an open, or alternative for linux serving, then I'm sure the dev's wouldnt mind too much (what with all th extra exposure). The problem is that its;
1. a shit load of work for us to reverse engineer, and then keep on top of changes to the netcode
2. we'd always be chasing Scawen (see: Samba, for instance)
I dont know if this has been pointed out recently, but Scawen has said in the past that his *ix experience isnt very vast, which is why we havent seen anything like this.
For reference, I'm totally willing to try the above (reverse engineering), or help out test compiling, running test builds, etc. I'm just a little short on time on too many occasions, what with work and my family life at the moment.