What do you think about something like this?
```python
    for version in mod.versions:
        delta = (datetime.now() - version.created).days // 60 + 1
        score += version.download_count() // delta
```
Instead of just adding the total download count of a mod to the score, this sums up the downloads per mod version, but the older the version the less value its downloads have.
In this example the Δscore per download is halved every 60 days, of course adjustable.