I just updated to the new version of Raspbian and the first thing I noticed was some new software. I'm wondering how these programs get to be on Raspbian & apt-get. Do you have to ask or are you invited/requested? for things bundled with Raspbian like the IDEs does the Pi foundation do that or GNU/Linux?
According to the Raspbian homepage, "Raspbian is not affiliated with the Raspberry Pi Foundation. Raspbian was created by a small, dedicated team of developers that are fans of the Raspberry Pi hardware, the educational goals of the Raspberry Pi Foundation and, of course, the Debian Project."
However, the most often used image is one created by the Foundation. Note the distinction here between "image" (those big files you burn onto SD cards) and "repository" (the place where the software in the image, and subsequent updates, come from).
Obviously there is some kind of close relationship between the two groups, but (unless they've just not bothered to update the web page), they are still independent of one another. I would like to believe that the Foundation helps to fund Raspbian, at least.
Raspbian is independent of Debian, and Debian is independent of GNU. There is no such organization as "GNU/Linux". "Linux" is a trademark of (and copyrighted by) its original creator, Linus Torvalds, and this official version is controlled by the Linux Kernel Organization, aka. kernel.org. In this proper sense, it refers to an operating system kernel, which is also used, e.g., on Android.
Linux is a Unix/POSIX style kernel, and the operating system colloquially referred to as "linux" combines it with POSIX (or "nearly POSIX") userland fundamentals developed and maintained by GNU, an organization which predates the linux kernel -- see here for some discussion of that. However, not all of the software included in Debian, etc., is a GNU product. Fundamental here refers to the native C library and various utilities minimally required for the proper functioning of a POSIX style OS. As an insight into what all that means, consider that Android, even though it uses the Linux kernel, is very far from being a "POSIX style" system, whereas OSX, which is (and always has been) completely independent from Linux and GNU, is certified compliant by POSIX (a real organization), as is Solaris (currently owned by Oracle). But all these myriad things all have roots in AT&T UNIX, and their similarities continue to be the result of active standardization intended to promote interoperability and make it easier for high level, end user software to be ported across the range.
Hence "GNU/Linux" is a more formal way to refer to an operating system (or tight knit family thereof) which combines technically compatible sets of software from two distinct organizations, something made easy by legally compatible open source licencing.
All GNU/Linux distributions are actually maintained by other independent bodies; GNU does not even have one -- although they have a close relationship with Debian.
Do you have to ask or are you invited/requested?
It could occur either way. If you have a piece of public FOSS software and a Debian packager (they are volunteers) takes interest in it and decides it would make a good inclusion, that person will probably contact you -- although the nature of FOSS licenses means this is not strictly necessary.
This could also be because of frequent requests by the user base. As far I am aware, anyone from that user base can become a volunteer at Debian, at least in some capacity.
It is more complicated the other way around since the repositories are controlled and this means someone involved must take responsibility for the package. How that plays out depends on your relationship with the packager, however, once a package is included, as long as you release updates via a public, stable location, updates of the package will be more or less automated as well.
The same general principles presumably apply to Raspbian, just on a smaller scale.
You need to make a distinction between Raspbian (nothing to do with the Raspberry Pi Foundation) and the image based on Raspbian which may be downloaded from the Raspberry Pi Foundation site (raspberrypi.org).
Raspbian is based on Debian and as far as I am aware only includes Debian packages.
The Raspberry Pi Foundation image is based on Raspbian but also includes packages created by the Foundation to further their educational aims.
An obvious example is Matheatica, others are NuScratch and gpioZero.
You can see if a package comes from Raspbian or the Raspberry Pi Foundation by running the following command. Note the web-site.
apt-cache policy package_name
$ apt-cache policy gcc gcc: Installed: 4:4.9.2-2 Candidate: 4:4.9.2-2 Version table: *** 4:4.9.2-2 0 500 http://mirrordirector.raspbian.org/raspbian/ jessie/main armhf Packages 100 /var/lib/dpkg/status $ apt-cache policy nuscratch nuscratch: Installed: 20160115 Candidate: 20160115 Version table: *** 20160115 0 500 http://archive.raspberrypi.org/debian/ jessie/main armhf Packages 100 /var/lib/dpkg/status