I don't suspect or accuse Kenko and his team of doing anything nefarious, but given that something as simple as a version launcher isn't open source, and that Rebuilt's source isn't public either is rather off-putting.
Given the history of this forum and its members, I don't think caution or even suspicion is an unreasonable reaction to any of this.
This is exactly my concern. I've almost been burnt twice with malicious software from here. The first was your run-of-the-mill backdoor blockland addon with an eval call hidden deep within. The second one was a program with actual professional RAT software nested inside. I think there was a malicious blockland web browser script floating around that used greasemonkey or something too but can't recall any posts about it.
The report I posted earlier is likely a bunch of false positives and I think Rebuilt is safe, after all, that's a lot of work to bait people into installing malware.