It's due to histrorical reasons - these is a quite lengthy story.
I'll summarize with my own words - as far as I know/remember/understood the history:
In the beginning Chris Mallet created AutHotkey - the AHK world was happy and unified. Later on Chris lost his motivation on further developing AHK - but the created world turned on. A few derivates of AutoHotkey arose, as there have been AHK_L by Lexikos and a few more variants - this led to a more or less splitted community with fiercy battles between AHK and AHK_L for example. Chris continued to retire from AutoHotkey, but as the creator of AutoHotkey, he still was the "highest" authority (as he maintained for example the domain www.autohotkey.com ...). Chris once realized that it's time to pass on the baton to keep the things going on. He took a look at the community to get appropriate successors (experience, reliability, activity ...) and presented candidates to the community and asked for volunteers. The end of the story was that Polyethene (yes - he had a good reputation within AHK community - and yes, he once was relieable and active ...) and a second person were chosen to be the successors. The main goal in the beginning was a reunification of the splitted AHK/AHK_L community and a modernization of the forum. But the two successors had different ideas of the way how to do it. After a while Polyethene decided - without consulting anybody (?)) - that it's time to show some activity. With a hush-hush operation he introduced the new forum software (as it is now) and proclaimed classic AHK as the one and only AHK, letting AHK_L just being a subordinate variant. Therefore the second nominated successor lost all his influence and was practically closed out with this coup - at last consequence he lost his motivation and retired completly from AHK (BTW: Has anybody heard anything from him lately?) Especially declaring classic AHK as successor of classic AHK led to some resistance among enthusiastic AHK-forum members, as classic AHK was a dead development with a few quirks, whilst AHK_L was a vivid development implementing some new ideas based on Lexikos and community ideas. An open letter was written to Polyethene which caused Poly to accept AHK_L as official successor of AHK ... Since then, Polyethene seems to be gone.
That's the current situation:
* Polyethene is the owner of the domain (autohotkey.com)
* Polyethene sponsors the domain
* Polyethene has bought and installed the current forum software
* Chris should know about the situation here within the forum, as he has contact to a few people here and is on the forum once a time. As he is "the AHK authority" and he does/can(?) not influence/stop (has no interest/possibilty (?)) Polyethene, the situation is as it is ...
* Lexikos does not have interest in this politics, he's interested in developing AHK (AHK_L) ...
* The community still struggles with the consequences of the historical split of AHK and AHK_L ..
AutoHotkey is theoretically community based. Practically AHK_L is open sourced and maintained by Lexikos, with very little community participation.
AutoHotkey forum isn't community based: domain and forum software are owned by Polyethene ... The forum lives from it's community - but community has no influence on forum design and so on ...