I've got Sideview Utils 2.4.8 installed, but in App Manager, it's asking me to update to 1.3.5.
Sounds like a bug. Can you send it in to Splunk support. I guess Splunkbase sees that you have a version that is newer than the version available on Splunkbase and it gets confused.
Is this 5.0? I'm pretty sure that in older Splunk releases this worked properly and it would not give you an 'update' link.
Yes, it's on Splunk 5.0.2. Will raise issue with Splunk support.