I'm not familiar with the Xbox 360 scene (IIRC they circumvented the DRM via the DVD reader, don't know if they achieved code execution other than the CPU bug exploit presented at the CCC) but I recall an official Microsoft SDK (XNA or something) that was distributed for a symbolic sum of money, Vita had an SDK built from scratch (vitasdk.org), at launch fat PS3 models could dualboot officially a generic PPC Linux distribution and Sony released documentation and tools that supported the Cell processor (but they blocked access to the GPU via the "hypervisor") and later was created an SDK from scratch (Psl1ght or something like that) and PS2 had a Linux kit that could be purchased separately (but still with crippled HW access, don't recall what wasn't supported) and again an SDK created from scratch that you can still find on Github even tho the ps2dev.org site went dark in 2010~2011...
Oh, yeah, I forgot XBMC for the original Xbox that still lives today as the Kodi mediaplayer.