The LibreOffice codebase is, to be frank, messy. This isn't a criticism of previous developers - it's still an amazing product and an amazing feat of programming given the number of platforms it runs on. The StarView guys, and later OpenOffice.org development team, did a great job. For instance, I was reading up on the font mapping code and I often saw Herbert Duerr's name, and I've got nothing but respect for the work that he did and his dedication to the project.
Unfortunately, the messiness is the result of a codebase that was first created in 1988 and has been actively worked on and changed directions a number of times. So... what is it that I love about working on LibreOffice?
In a word: the people. I've never met any of my fellow hackers in person, only a few phone calls to Michael Meeks and listened in on some Collabora meetings when I did some work for them. Mostly I stick around the IRC channel and keep an eye on the mailing list.
On the IRC channel, however, I've noticed the good humour and tolerance of the developers towards those not as expert as themselves. For example, Stephan Bergman (sberg) is the go to guy in terms of anything C++ related - and the other day he helped me out with a tricky bit of code (well, I thought it was tricky) related to the equality operator. Tor Lillqvist, as another example, is a diamond in the rough IMO and has often pointed me in the right direction when I'm online. And I cannot forget to mention Norbert Thiebaud (shm_get on IRC) for his constant maintenance of Jenkins (a thankless task!) and gerrit. These are literally just some of the folks who I interact with all the time and just a small sample of the folks who work on the LibreOffice project.
Without the goodwill and encouragement of the folks who hack away daily on the LibreOffice project, I doubt I'd be able to work on the small part of the codebase that I have chosen to improve. In fact, there is an active outreach program currently being run lead by Jan Iverson (JanIV on IRC) and there are quite a few commits coming in from newbies of all stripes. This is leading to some real improvements in the code, for instance new developer Dipankar Niranjan did a whole series of commits to remove the "dog-tag" code from the VCL module (the "dog-tags" was a way of attempting to ensure that Windows weren't deleted at the wrong time, but was a total hack and has been solved by VclPtr) - this has recently allowed sberg to remove ImplSVEvent::maDelData. Seeing the code evolve is also highly enjoyable :-)
There are so many more examples of this it's just not possible for me to list them in this post. It's interesting that LibreOffice has made so much traction in the last year in terms of code quality - whilst the UI hasn't changed hugely (though that is going to change I suspect in the next year!) the incremental improvements have been increasing at a rate of knots and folks are beginning to notice the positive effects. One user, who will remain nameless but is an active follower of the LibreOffice development process, told me that he noticed that the 5.x release was very much more responsive and stable that the 4.x series... and amusingly commented that "it's remarkable how interesting it is to watch the development of such an intrinsically boring type of software".
So there you have it, the reason I love hacking at LibreOffice is the people who work on it! May it ever be this way.