"There is no problem" [insert Jedi mind trick here]. I think he's already provided a counterexample to this, assuming he's speaking from his own experience. It's difficult to remember how nonsensical all this could be to someone who is unfamiliar and/or has never been involved in development. This can happen with any topic because a word without background or context begins as absolute nonsense.
Here's a quick stab at it.
diffs - After a programmer modifies sourcecode, a diff can be generated to succinctly describe the difference between the old version and the modified version. This is often associated with cvs. If you're not a developer and are not fairly familiar with building/compiling your own executables (such as is often done in *nix environments), then you don't want to deal with these unless you want to get more deeply involved (it could take some sustained effort). In the case of dosbox, this often involves small fixes that will eventually be integrated into someone's build anyway if it's good.
frontend - menu for configuring settings and launching an application. In the case of dosbox, it generally means that after initial configuration, you can run a game with the best settings just by clicking on it. It's popular with people who don't want to get involved in technical details, and perhaps with people who are obsessed with collection and/or organization.
cvs - programmers store their sourcecode in here while developing. Other programmers can grab from it, and approved programmers are allowed to contribute into it. Anyone can grab it actually... but if you do, then it is only useful to you if you know how to compile it into an executable. If you're not a developer and are not familiar with *nix, then you probably don't want to build it. Some nice people periodically grab the cvs sourcecode and create recent builds and make them available for download.
syntax - well, you could use a dictionary to get a start at this one 😀 Beyond that.. If you're a moderate computer user, you should be comfortable opening a text configuration file in notepad and changing some values. You can make a backup and experiment with this. If you're not comfortable with it, then you can use a frontend.