There are surely less threads in the Sailfish/Jolla forums, but they are younger than other TMO sub-forums, and there is still a lot of activity (also in the Applications forum). To be honest, together.jolla.com is useful, but I doubt it will totally replace TMO, and hope it won't. Plus the TJC application is less advanced than the TMO one (it seems to basically display HTML inside an app, with associated issues for easy browsing with tiny buttons).

I can't help, no dev skills, but I hope someone will raise his hand then!