virtualbox.org

mtr wrote:Are there are other sources?

google search wfw31.zip yields numerous possibilities

mtr wrote:This is no longer an option from AMD.

Are there are other sources?

Yes, AMD. The driver is (as of October 2014) hidden in plain sight at http://support.amd.com/en-us/search/utilities

With all the interest in DOS networking I tried this on FreeDOS 1.2 (current version, fresh download) as well. Go for a full FreeDos install, set up networking and modify FDCONFIG.SYS as follows:

insert:

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12?DEVICEHIGH=C:\NET\IFSHLP.SYS

after:

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34?SHELL=C:\FDOS\BIN\COMMAND.COM C:\FDOS\BIN /E:1024 /P=C:\AUTOEXEC.BAT

and before:

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12?SHELLHIGH=C:\FDOS\BIN\COMMAND.COM C:\FDOS\BIN /E:1024 /P=C:\AUTOEXEC.BAT

which makes the result look like (only end of file is shown):

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.......
124?DOS=HIGH
12?DOS=UMB
124?DOSDATA=UMB
1?DEVICE=C:\FDOS\BIN\JEMMEX.EXE NOEMS X=TEST I=TEST NOVME NOINVLPG
234?DEVICE=C:\FDOS\BIN\HIMEMX.EXE
2?DEVICE=C:\FDOS\BIN\JEMM386.EXE X=TEST I=TEST I=B000-B7FF NOVME NOINVLPG
34?SHELL=C:\FDOS\BIN\COMMAND.COM C:\FDOS\BIN /E:1024 /P=C:\AUTOEXEC.BAT
12?DEVICEHIGH=C:\NET\IFSHLP.SYS
12?SHELLHIGH=C:\FDOS\BIN\COMMAND.COM C:\FDOS\BIN /E:1024 /P=C:\AUTOEXEC.BAT

Use option 2 to boot....

I tried this on an Ubuntu system with VirtualBox 4.3.36; need NAT interface to get it going (usually I succeed in using Host-Only Interface). For the rest: you can check the FreeDos site for options and also this one:
https://wiki.samba.org/index.php/Configuring_FreeDOS_to_Access_a_Samba_Share