It looks like there's a difference between
Project Radium and
Radium Core. The core blog is very active -
https://blog.radiumcore.org/Also, frequency of GitHub commits is a common misnomer. If you take a peek at their development process (
https://github.com/RadiumCore/Radium), you can see that developers don't commit directly to the core repo:
Developers work in their own trees, then submit pull requests when they think their feature or bug fix is ready.
The patch will be accepted if there is broad consensus that it is a good thing. Developers should expect to rework and resubmit patches if they don't match the project's coding conventions (see coding.txt) or are controversial.
Edit: Also looks like
https://radiumcore.org/ is down. I definitely was able to visit this yesterday. dbt1033 you killed their site with new traffic

The more I think about it, the more I think "activity" is less and less important in judging a project's crypto performance in terms of price. If anything can be learned, it seems that the devs who quietly work behind the scenes and post regular updates are the ones building strong products. Their linked crypto seldom follows the trend in price though.
Then there are those devs who talk a lot and work hard to chat with community, encouraging listing on exchanges and actively engaging in pumps.
There is no fixed rule for crypto.