Due to popular demand, Stella has moved off of Sourceforge and to Github. The new address is https://stella-emu.github.io. There's a link at the old website that points to this, but all Sourceforge related stuff will be removed in approx. 3 months. Many people have been experiencing issues with Sourceforge, so hopefully this will fix the issues. If you visit other websites that mention Stella, please consider asking them to update their links.
For developers, we've moved from using Subversion to Git. The new Stella webpage includes updated instructions on how to checkout with Git. If you're not familiar with Git, now is the time to learn The developer page is at https://github.com/stella-emu/stella.
Finally, we're in the middle of releasing test builds for the upcoming 5.0 release. These can be checked out at https://github.com/s...stella/releases.
Let me know if there are any issues. Since Stella has used Sourceforge for almost 15 years, it's possible I missed something in the changeover (but hopefully not).
EDIT: Github also has a very nice facility for reporting bugs (called issues), and tracking the progress of fixing these issues. There was a similar feature on Sourceforge, but it was much harder to use. Please consider using this for reporting bugs, as it's much easier to have them all documented in one place.