TeX Live is included in a number of system distributions (“distros”). TL was originally conceived and is still distributed as a benefit of the TeX user groups, including prebuilt binaries and independent of any specific operating or packaging system, but we are glad to see it being used as the basis of the TeX installation in other systems.
We have a mailing list specifically for discussion of TL integration in distros: tldistro@tug.org. Feel free to post, join, or peruse the archives if you are interested.
System distributions have their own packaging systems, so tlmgr is not used for TeX-related package updates by distros.
If you are considering (re)packaging TeX Live, then carefully consider how to handle fmtutil and updmap programs (often used directly), and hyphenation patterns (maintained via tlmgr generate language in native TL), among many other things. Purely as an example of one distro's choices, you may wish to peruse the TeX-on-Debian and Debian-TeX-Policy documents. (We have no opinion pro or con about Debian or TeX on Debian; we're merely noting that they have written up many decisions that anyone creating a TeX distribution needs to make.)
You can get the stable TL releases as tarballs from tug.org, which you may find easier to deal with than ISO images. Please try to minimize downloads of these big files from our central server.
Here is a list of distros and their respective maintainers, to the best of our knowledge.
Please send corrections to tldistro@tug.org.
Again, please send additions to tldistro@tug.org.