Found this version of Yadex online.

https://github.com/farhaven/yadex

But this will not work properly at all. I load the Doom IWAD and the map I want to edit and I get this crash dump when I hit enter.

homer@deep-thought ~/Documents/basenew $ yadex -g doom -file basenew.wad
Yadex 1.7.1 (2012-06-20)
Reading config file "/etc/yadex/1.7.1/yadex.cfg".
Reading config file "/home/homer/.yadex/yadex.cfg".
Reading game definition file "/usr/local/share/games/yadex/1.7.1/doom.ygd".
Loading iwad: /usr/local/share/games/doom.wad...
Loading pwad: basenew.wad...
  Levels: E4M1

** Welcome to Yadex. Glad you've made it so far. :-)
**
** This version is believed to be stable but you never
** know so make backup copies of your data anyway.
**
** Yadex is work in progress. Subscribe to yadex-announce
** or keep an eye on the web page.
** To edit an existing level, type "e <level_name>".
** To create a new level, type "c".

yadex: e 41
*** buffer overflow detected ***: yadex terminated
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(__fortify_fail+0x5c)[0x7fef6dd155cc]
/lib/x86_64-linux-gnu/libc.so.6(+0x110560)[0x7fef6dd14560]
/lib/x86_64-linux-gnu/libc.so.6(+0x10fc6b)[0x7fef6dd13c6b]
/lib/x86_64-linux-gnu/libc.so.6(__snprintf_chk+0x78)[0x7fef6dd13b48]
yadex[0x40d3ab]
yadex[0x44fdac]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5)[0x7fef6dc25ea5]
yadex[0x403a29]
======= Memory map: ========
00400000-00467000 r-xp 00000000 08:61 6561183                            /usr/local/bin/yadex-1.7.1
00666000-00667000 r--p 00066000 08:61 6561183                            /usr/local/bin/yadex-1.7.1
00667000-00669000 rw-p 00067000 08:61 6561183                            /usr/local/bin/yadex-1.7.1
00669000-0066a000 rw-p 00000000 00:00 0 
01951000-01993000 rw-p 00000000 00:00 0                                  [heap]
7fef6d1c2000-7fef6d1c7000 r-xp 00000000 08:61 6036770                    /usr/lib/x86_64-linux-gnu/libXdmcp.so.6.0.0
7fef6d1c7000-7fef6d3c6000 ---p 00005000 08:61 6036770                    /usr/lib/x86_64-linux-gnu/libXdmcp.so.6.0.0
7fef6d3c6000-7fef6d3c7000 r--p 00004000 08:61 6036770                    /usr/lib/x86_64-linux-gnu/libXdmcp.so.6.0.0
7fef6d3c7000-7fef6d3c8000 rw-p 00005000 08:61 6036770                    /usr/lib/x86_64-linux-gnu/libXdmcp.so.6.0.0
7fef6d3c8000-7fef6d3ca000 r-xp 00000000 08:61 6036757                    /usr/lib/x86_64-linux-gnu/libXau.so.6.0.0
7fef6d3ca000-7fef6d5ca000 ---p 00002000 08:61 6036757                    /usr/lib/x86_64-linux-gnu/libXau.so.6.0.0
7fef6d5ca000-7fef6d5cb000 r--p 00002000 08:61 6036757                    /usr/lib/x86_64-linux-gnu/libXau.so.6.0.0
7fef6d5cb000-7fef6d5cc000 rw-p 00003000 08:61 6036757                    /usr/lib/x86_64-linux-gnu/libXau.so.6.0.0
7fef6d5cc000-7fef6d5cf000 r-xp 00000000 08:61 2625194                    /lib/x86_64-linux-gnu/libdl-2.17.so
7fef6d5cf000-7fef6d7ce000 ---p 00003000 08:61 2625194                    /lib/x86_64-linux-gnu/libdl-2.17.so
7fef6d7ce000-7fef6d7cf000 r--p 00002000 08:61 2625194                    /lib/x86_64-linux-gnu/libdl-2.17.so
7fef6d7cf000-7fef6d7d0000 rw-p 00003000 08:61 2625194                    /lib/x86_64-linux-gnu/libdl-2.17.so
7fef6d7d0000-7fef6d7ed000 r-xp 00000000 08:61 6032320                    /usr/lib/x86_64-linux-gnu/libxcb.so.1.1.0
7fef6d7ed000-7fef6d9ec000 ---p 0001d000 08:61 6032320                    /usr/lib/x86_64-linux-gnu/libxcb.so.1.1.0
7fef6d9ec000-7fef6d9ed000 r--p 0001c000 08:61 6032320                    /usr/lib/x86_64-linux-gnu/libxcb.so.1.1.0
7fef6d9ed000-7fef6d9ee000 rw-p 0001d000 08:61 6032320                    /usr/lib/x86_64-linux-gnu/libxcb.so.1.1.0
7fef6d9ee000-7fef6da02000 r-xp 00000000 08:61 2625204                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7fef6da02000-7fef6dc02000 ---p 00014000 08:61 2625204                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7fef6dc02000-7fef6dc03000 r--p 00014000 08:61 2625204                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7fef6dc03000-7fef6dc04000 rw-p 00015000 08:61 2625204                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7fef6dc04000-7fef6ddc2000 r-xp 00000000 08:61 2625179                    /lib/x86_64-linux-gnu/libc-2.17.so
7fef6ddc2000-7fef6dfc1000 ---p 001be000 08:61 2625179                    /lib/x86_64-linux-gnu/libc-2.17.so
7fef6dfc1000-7fef6dfc5000 r--p 001bd000 08:61 2625179                    /lib/x86_64-linux-gnu/libc-2.17.so
7fef6dfc5000-7fef6dfc7000 rw-p 001c1000 08:61 2625179                    /lib/x86_64-linux-gnu/libc-2.17.so
7fef6dfc7000-7fef6dfcc000 rw-p 00000000 00:00 0 
7fef6dfcc000-7fef6e0cf000 r-xp 00000000 08:61 2625227                    /lib/x86_64-linux-gnu/libm-2.17.so
7fef6e0cf000-7fef6e2cf000 ---p 00103000 08:61 2625227                    /lib/x86_64-linux-gnu/libm-2.17.so
7fef6e2cf000-7fef6e2d0000 r--p 00103000 08:61 2625227                    /lib/x86_64-linux-gnu/libm-2.17.so
7fef6e2d0000-7fef6e2d1000 rw-p 00104000 08:61 2625227                    /lib/x86_64-linux-gnu/libm-2.17.so
7fef6e2d1000-7fef6e3b6000 r-xp 00000000 08:61 6037661                    /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.17
7fef6e3b6000-7fef6e5b5000 ---p 000e5000 08:61 6037661                    /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.17
7fef6e5b5000-7fef6e5bd000 r--p 000e4000 08:61 6037661                    /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.17
7fef6e5bd000-7fef6e5bf000 rw-p 000ec000 08:61 6037661                    /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.17
7fef6e5bf000-7fef6e5d4000 rw-p 00000000 00:00 0 
7fef6e5d4000-7fef6e708000 r-xp 00000000 08:61 6031107                    /usr/lib/x86_64-linux-gnu/libX11.so.6.3.0
7fef6e708000-7fef6e908000 ---p 00134000 08:61 6031107                    /usr/lib/x86_64-linux-gnu/libX11.so.6.3.0
7fef6e908000-7fef6e909000 r--p 00134000 08:61 6031107                    /usr/lib/x86_64-linux-gnu/libX11.so.6.3.0
7fef6e909000-7fef6e90e000 rw-p 00135000 08:61 6031107                    /usr/lib/x86_64-linux-gnu/libX11.so.6.3.0
7fef6e90e000-7fef6e931000 r-xp 00000000 08:61 2625155                    /lib/x86_64-linux-gnu/ld-2.17.so
7fef6eb04000-7fef6eb0b000 rw-p 00000000 00:00 0 
7fef6eb29000-7fef6eb30000 rw-p 00000000 00:00 0 
7fef6eb30000-7fef6eb31000 r--p 00022000 08:61 2625155                    /lib/x86_64-linux-gnu/ld-2.17.so
7fef6eb31000-7fef6eb33000 rw-p 00023000 08:61 2625155                    /lib/x86_64-linux-gnu/ld-2.17.so
7ffff3844000-7ffff3865000 rw-p 00000000 00:00 0                          [stack]
7ffff39c9000-7ffff39cb000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]

Are there any good editions of Yadex that will compile and work correctly on a modern installation of x64 Linux? I know about Eureka, but I want to use Yadex.

I think that Yadex has some problems when compiled as 64-bit. Compiling it as 32-bit might help. There are a whole bunch of patches floating around to fix various bugs and I don't know if this version has applied them all.

You typed 'e 41' to edit E4M1. Have you tried 'e 4 1' instead?

I can't really tell what this guy changed in the code. But anyway, I've been using the old Yadex 1.7.0 on OpenBSD/amd64 so it should run on Linux too. Just grab the 64-bit clean diff's from the FreeBSD ports:
http://www.Freshports.org/games/yadex

hex11 said:

I can't really tell what this guy changed in the code.

You can't read the git history on that page?