The companion version refers to the version of the software running on your phone or tablet. Today, the published version in the Google Play Store is version 2.65. Because Google prevents us from including some features in that version, we also publish another version via the Help > Companion Information dialog with the 'u' suffix to indicate it is unencumbered by the Google requirements. This version is needed to test some features like direct SMS messaging/phone calls. Users of earlier versions may continue to use App Inventor but we make no guarantees that newer features work on the older companion versions.
The website versioning is independent of the companion version and is available via the Help > About menu. Currently the website version is nb190b.
Thanks for the answer. My problem is with the English used in this sentence, where All Words Are Capitalized, and there seem to be missing commas, new lines, periods, whatever. I can't parse it...
Companion Version Use Companion: 2.65 or 2.65u
In fact, the part Use Companion: 2.65 or 2.65u comes straight from the About popup and seems to be simply appended to the Companion Version part. Maybe it worked in the past and looked OK, but something is broken when (dynamically?) composing this sentence.
Maybe something like this would make more sense:
Use Companion versions: 2.65 or 2.65u Requires Companion: 2.65 or 2.65u