I don't think that's the case.
"Thunderbird is part of MZLA Technologies Corporation, a wholly owned subsidiary of Mozilla Foundation."
Thunderbirds sourcecode is literally part of the same mercury codebase as Firefox.
Thunderbird does have a very small team, and I think everyone that uses it should considering donating.
(Also, someone help a non-native speaker: I think the "effect"s above should be "affect", but for some reason that looked wrong here. Why is that?)
and technology choices made in Firefox can and do affect Thunderbird, just like they effect e.g. Zen Browser or Tor Browser.
English is a bit of a bastard language IIUC, and so we accept the way you've phrased it too, but in that case it should be "affect".
I hope this helps rather than making things more confusing! ;)
It's definitely wrong in that paragraph.
However, both have alternative meanings as the other part of speech.
Affect as a noun means emotion or disposition, and is mostly used in psychology. Your psychologist may say you have a depressed affect.
Effect as a verb means to bring about. You might say that a successful protest effected change in society.
As a verb, in addition to “have an impact on,” affect can also mean “to pretend to have,” like “she affected an air of mystery,” although this is less common.
The way you used "effect" here, its verb sense of "to bring about or cause" is the one that suggests itself, which isn't what you meant.
The simple way to keep the words' overlapping meanings straight, is that it's "effect" when it's a noun, "affect" when it's a verb. "Effect" can also be a verb, and "affect" can be a noun, but those definitions don't overlap.
Your post did indeed call for "affect", as you suspected.
Edit: hmm, re-reading it now, affect does look right. Weird.