Yes sure did, I was working in a compagny where the base product OS was RH 6.5 and I had to rework the bootloader for enhanced failsafe hardware boot feature, I also created some hardware related drivers and also rework the init process for memory initialisation of the product. That was 10 years ago!!!

The password and blacklist plugins for roundcube. I made the password plugin refuse passwords that are easily cracked (I used zxcvbn for that) and changed the blacklist plugin to work as a whitelist instead.

Semi-colon-like fixes for ethercalc, tiki-wiki.

A one-line fix for bottle.py to make it properly timeout.

When actively contributing code to an active opensource project counts as yes, then yes.
Else when submitting patch to kernel module count as yes, then yes.
Otherwise, break

I once needed to edit the code of a program which was too fast to adopt stupid libappindicator tray icon behaviour in fact ditching the context menu functionality. it was a very minute change, and I used it on my machine only, but it was totally worth the effort and I enjoyed it

Yes.
Modified bootloader, Ethernet driver to process control message of base station in kernel space, etc. It was five years ago when I was working for a big telecom company to provide common platform service for different broadband network components. It is kind of PaaS in old fashion.

I am a simple user, not a coder.

I have never "modified the source code of an open source application".
BUT....

..... I HAVE programmed in Basic, Pascal, C, DOS, Unix/Linux Shell, SQL, MS Access, Python.
..... I HAVE used graphical code debuggers that trace the code execution visually line by line, loop by loop.
..... I HAVE compiled code into applications for use on different systems

sooOOoo .... what difference does it make if it's 'Open source applications' ?

Am I missing something here?
Just curious.

I have added some more logging to Asterisk in cases where it really didn't tell you why certain SIP messages were being rejected. I never passed this back up the chain.

No, I have only very little coding experience and none in C or C++.

I am a co-maint of perl5 so I commit changes on a somewhat regular basis.
I also made changes (that were accepted) in xterm, elvis, claws-mail, tcsh, grep, gcc and other OSS

Yes, examples: several shell scripts (mostly installers), Apache Hue, currently working on a package for http://hackage.haskell.org/ .

Yes.

In my case, I modified xterm to provide a feed to a custom log fifo file, and to include the edits done (filtering backspaces/character removal) from the log output. The output was recieved via the fifo by a logging process to timestamp and format the log.

This was used to provide a consolidated log of activity from a multiple of console lines connected to various computers.

This also required modification of window manager to allow more than the default number of 32 root windows - the modification could allow any number, generated at compile time in multiples of 32 workspaces.

The log could then be used to locate the source of various system problems where the origin of the problem might not be the system that reported it. It also captured hardware messages that could not be captured by syslog (as these failures tended to occur when disks and any other computation services - like syslog requires). It also would catch any cascading failures as well.

The resulting system (there were two) provided a consolidated console log for up to 64 systems though the usual number was between 24 and 35... (file servers, mail servers, Kerberos servers, compute servers...)

I did a lot of big changes to code I used for myself without giving it back to the community, but also contributed some small changes and patches to fix open issues to several projects. For one specific open source project I provided support for ARM and Raspberry Pi for a while.

Yes. An offline dictionary and a video DVD authoring tool.

I have. Not very often but, some libraries I use need some tweaking to work. I try to submit changes upstream.

My personal RPi server runs my version of a media player that is based on an open-source player.

Needless to say. An interesting poll.