sdlBasic havent been developed for a long time. Also it's forums are mostly spammed and ruined by bot's. Rumours does say, that author has lost his interest to develope this dialect because real life keeps him too busy.
QB64 is developing with nice speed. More or less major and important updates are released every few weeks. Latest windows release (v. 0.922) was released October 20'th. Linux versions comes a bit behind, but they do come.
ThinBasic forums are moved under VBulleting software. Community seems to be happy with the change in general.